1 whitefish fillet per person (I used tilapia, since it's a bit meatier)
Olive oil, for the pan
1 small onion, diced
Salt and pepper, to taste
1/2 cup white wine
1 15oz can low sodium diced tomatoes, with juice
1 8oz can chopped pitted black olives
2 tbs capers, rinsed
1/4 tsp red pepper flakes
2 cups chopped spinach leaves
Optional: crumbled feta cheese to serve