This easy and tasty savory sardine tart should definitely be in your summer dinner rotation. Paired with a gorgeous green salad on the side, it's the perfect light and healthy meal. For this recipe, brown 1 chopped onion in a buttered skillet, add a small can of tomato paste and 1 whole diced tomato. Heat the mixture through, and set aside. Roll out your prepared puff pastry crust, and add the tomato preparation, 1 1/2 cups grated Swiss cheese, a can of sardines (drained) and 5 sliced green olives. Bake for 25 to 30 minutes at 350° F, and serve immediately.