Sandwiches with tomatoes and onions

100 g butter
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8 slices of bread

5 heads of onions

2 tomato

2 tbsp. tomato paste

greens

mustard

salt

Beat butter, add finely chopped onion and tomato paste, stir well.

Spread the mixture on 4 slices of bread, cover with the remaining.

Before serving sandwiches with tomato and onion garnish with sliced tomatoes.