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Tuna in mushroom caps turns a few cans of tuna into an elegant, bread-free stuffed dinner. Yellowfin tuna, capers and garlic fill meaty portobello caps that roast in a hot oven until tender. Thin avocado slices finish each cap like a little crown.
Pro Tips
- Drain the tuna thoroughly before mixing — wet filling steams the mushroom caps instead of roasting into them.
- Mix the tuna with the garlic powder, black pepper and rinsed capers first so the seasoning is even before stuffing.
- Bake at a hot 450 degrees for 15-20 minutes; the caps are ready when they brown and turn somewhat tender.
- Slice the avocado thin and add it only as garnish after baking, so it stays cool and creamy against the hot mushroom.
- For a different twist, swap the avocado garnish for raisins or fresh dill — both are lovely with the capers.
Frequently Asked Questions
Can I use tuna packed in water instead of oil?
Yes — just drain it well. Tuna in oil gives a richer filling that matches the meaty portobello, but water-packed works with the same method.
Can I stuff the caps ahead of time?
Absolutely — assemble them on the tray, refrigerate, and bake when ready. Add a couple of minutes to the bake if they go in cold.
How do I know when the mushrooms are done?
They'll brown around the edges and turn tender through the middle after 15-20 minutes at 450 degrees. Give one a gentle press — it should yield without being limp.
What should I serve alongside?
A crisp green salad with lemon vinaigrette keeps the plate light, or roasted vegetables for something more substantial.
Recipe Card

Ingredients
Method
- 1.
- Preheat oven to 450° F.
- 2.
- Mix tuna, garlic powder, black pepper and capers together in a bowl
- 3.
- Stuff the tuna mixture unto the portobello caps.
- 4.
- Arrange the portobello caps on a lightly greased baking tray and bake for 15-20 minutes. You can also wait for the caps to turn brown and become somewhat tender, as a sign that they are cooked.
- 5.
- Slice open the avocado, remove the seed.
- Slice the meat into thin slices and add them to the portobello caps as garnish.
- 6. You can change the avocado into raisins or dill for a different taste.




