Step 1

1 Preheat the oven to 400°F (200°C). Chop onion, bell pepper and celery finely and fry in butter in a large frying pan until slightly soft. Season with salt and pepper.

Step 2

2 Mix tuna, mayonnaise, parmesan cheese and chili flakes in a greased baking dish. Add fried vegetables and stir.

Step 3

3 Bake for 15-20 minutes or until golden brown.

Step 4

4 Serve with baby spinach and olive oil.