Tuna Noodle Casserole

Let’s be honest, nothing screams childhood nostalgia quite like a bubbling hot dish fresh out of the oven, but I wanted a version that didn’t leave me feeling weighed down. This Dairy-Free Tuna Noodle Casserole is my absolute go-to when I need healthy comfort food that actually satisfies. By swapping heavy pasta for fresh zucchini noodles and using a rich, savory coconut sauce, you get all that classic creamy flavor without the dairy or the carb crash. It’s the perfect cozy weeknight dinner that proves you don’t have to sacrifice taste to eat well!

Serves: 8

Ingredients

• Coconut oil for greasing (approx. 0.5 tbsp / 7 g)

• Sea salt and pepper to taste

• 12 oz (340 g) julienned zucchini or prepared spaghetti squash

• 15 oz (425 g) solid white tuna in water (3 cans), drained thoroughly

• 0.7 tbsp (10 ml) olive oil

• 0.7 tbsp (10 g) coconut oil, divided use

• 0.7 tbsp (10 ml) fresh-squeezed lemon juice

• 10 oz (285 g) white mushrooms, trimmed and sliced 0.25-inch thick

• 1 onion, chopped fine (approx. 6 oz / 170 g)

• 24 fl oz (710 ml) Chicken Broth or Stock

• 12 fl oz (355 ml) coconut milk

• 4 fl oz (120 ml) water

• 2 tbsp (16 g) tapioca or arrowroot flour

• 7 oz (200 g) Coconut Milk Cheddar Cheese, shredded

• 5 oz (140 g) frozen spinach, thawed and drained (approx. 1 cup)

• 3 oz (85 g) White Sandwich Breadcrumbs, toasted (approx. 1 cup)

Preparation

1. Adjust the oven rack to the middle position and preheat the oven to 425°F (220°C). Grease a 9×13-inch (23×33 cm) baking dish with a small amount of coconut oil.
2. In a mixing bowl, combine the 15 oz (425 g) of tuna, 0.7 tbsp (10 ml) olive oil, 0.7 tbsp (10 ml) lemon juice, approx. 0.1 tbsp sea salt, and 0.1 tbsp pepper. Flake the tuna into coarse pieces with a fork and let it sit for 10 minutes.
3. Julienne the zucchini to create “noodles.” Place the 12 oz (340 g) of noodles on a lightly greased baking sheet. Sprinkle lightly with sea salt and pepper. Place in the oven and bake for 5 to 10 minutes, or until the noodles release much of their moisture but remain firm (not burned). Remove and set aside. (Note: If using prepared spaghetti squash instead of zucchini, skip this oven step).
4. Over medium-high heat, heat 0.35 tbsp (approx. 5 g) of coconut oil in a nonstick skillet until shimmering. Add the sliced mushrooms and chopped onion. Cook until the liquid evaporates and the mushrooms are browned, typically 5 to 7 minutes.
5. Whisk in the 24 fl oz (710 ml) of broth and 12 fl oz (355 ml) of coconut milk, scraping up any browned bits from the pan, and bring to a simmer.
6. In a small bowl, combine the 4 fl oz (120 ml) of water and 2 tbsp (16 g) of arrowroot or tapioca flour. Whisk this mixture into the pot. Continue to simmer, whisking constantly, until the sauce is slightly thickened, about 3 minutes.
7. Remove the skillet from the heat. Whisk in the 7 oz (200 g) of cheese, a handful at a time, until fully melted. Stir in the cooked zucchini noodles (or spaghetti squash), the seasoned tuna mixture, the drained spinach, 0.2 tbsp sea salt, and 0.2 tbsp pepper.
8. Transfer the mixture to the prepared baking dish. In a small bowl, toss the 3 oz (85 g) of toasted breadcrumbs with the remaining 0.35 tbsp (5 g) of melted coconut oil. Season with salt and pepper to taste.
9. Sprinkle the breadcrumb mixture over the top of the tuna mixture. Bake until the sauce is bubbling around the edges, approximately 12 to 14 minutes. Allow the casserole to cool slightly before serving.

Nutritional Information Per Serving

• Calories: 290 kcal

• Total Fat: 16g

• Total Carbohydrates: 23g

• Dietary Fiber: 2g

• Sugars: 2g

• Protein: 14g

• Cholesterol: 15mg

• Sodium: 480mg

Pro Tips for the Perfect Casserole

• Don’t Skip the Pre-Bake: The secret to avoiding a watery casserole is handling the zucchini correctly. Zucchini is mostly water! That pre-baking step is crucial to draw out moisture before it hits the sauce. If they still look “weepy” after coming out of the oven, pat them gently with a paper towel before adding them to the skillet.

• The “Slurry” Secret: When adding the tapioca or arrowroot flour, always mix it with the cold water first to create a smooth liquid (a slurry) before dumping it into the hot pan. If you toss dry powder directly into the hot broth, it will clump up instantly and be impossible to smooth out.

• Drain the Tuna Aggressively: “Drained thoroughly” means drained thoroughly. Press the lid of the can down into the sink to squeeze out every last drop of water. Any extra liquid from the tuna will dilute your creamy coconut sauce.

• Cheese Melting Magic: Dairy-free cheeses (like the Coconut Milk Cheddar used here) melt differently than traditional dairy. They often take a little longer or need lower heat to avoid becoming oily. Stir it in gradually off the heat, just as the recipe states, for the smoothest texture.

• Storage Savvy: Because arrowroot and tapioca are starches that can change texture when reheated, this dish is best eaten fresh. However, if you do meal prep, store the sauce/tuna mixture separately from the zucchini noodles and combine them just before baking to keep the texture fresh.

Frequently Asked Questions

Can I freeze this dairy-free tuna noodle casserole? It is not recommended to freeze this particular dish. Zucchini noodles tend to release a significant amount of water when thawed, which will make the casserole soggy. Additionally, sauces thickened with tapioca or arrowroot starch can sometimes separate or become gelatinous after freezing and reheating. For the best texture, enjoy this dish fresh or store it in the refrigerator for up to 3 days.

How do I prevent the zucchini noodles from making the casserole watery? The most important step is the “pre-bake.” By roasting the spiralized zucchini for 5 to 10 minutes before adding it to the sauce, you evaporate the excess moisture that would otherwise leak out during the final bake. If you are short on time, you can also salt the noodles and let them sit in a colander for 20 minutes, then squeeze them tightly with a kitchen towel.

Can I use a different flour to thicken the sauce? Yes, if you don’t have tapioca or arrowroot flour, you can use cornstarch (corn flour) in the same amount. If you are not strictly grain-free, regular all-purpose flour works as well, though you may need slightly more (about 3 tablespoons) to achieve the same thickness.

What can I use instead of white sandwich breadcrumbs? If you want to keep this recipe gluten-free or lower in carbs, you can substitute the white breadcrumbs with crushed pork rinds or almond flour mixed with a little nutritional yeast. This adds a nice crunch and savory flavor without the gluten or extra carbohydrates.

Can I swap the tuna for another protein? Absolutely. This recipe works very well with canned chicken or leftover shredded rotisserie chicken. If you prefer seafood but want a change from tuna, canned salmon is a great alternative that pairs nicely with the creamy coconut sauce and dill.

I hope this Dairy-Free Tuna Noodle Casserole becomes a regular in your dinner rotation just like it is in mine. It’s proof that you can crave that bubbling, cheesy texture and still stick to your health goals without feeling deprived. If you give this recipe a try, I’d love to hear about it! Leave a comment below letting me know how it turned out, or tag me on Instagram so I can see your delicious creation. Happy cooking!