Chop the onion and garlic and fry in a pan with 1 tablespoon of olive oil until translucent. Peel the tomatoes and add them, reduce slightly. Season with salt, pepper and the herbs and mix in the olives. Add a pinch of sugar. Put everything in a baking dish.
Cut the fish into large cubes and drizzle with lemon juice. Put on the tomato sauce. Dice the sheep cheese, crumble and spread on top.
Bake in a hot oven at 160 ° C top / bottom heat for approx. 20 - 30 minutes.