Wash, seed and dice the tomatoes. Peel onions, dice 1 light one. Fry everything with seeds in 1 tablespoon of oil for 2-3 minutes, season
Clean and leafy mushrooms, cut olives into slices. Fry mushrooms in 1 tbsp. hot oil for 2-3 minutes, season. Stir in wine and olives
Wash the arugula, pluck finely. Finely chop 1 onion. Drain tuna, pluck. Mix everything. Season with salt, pepper and lemon
Cut the bread into 12 slices and sprinkle with 2-3 tablespoons of oil. Roast in a coated pan or in the oven. Spread the seasoning masses on top