For the tuna pizza, preheat the oven to 200 degrees. Drain the tuna. Spread the pizza dough with Pesto Rosso. Cut the mozzarella into slices.
Peel the onions and cut them into half rings. Spread the tuna on the pesto rosso. Top with onions and mozzarella slices. Then sprinkle the capers on top. Season with salt and pepper.
Place the pizzas in a preheated oven at 200 degrees and bake for about 12 minutes. Then drizzle with a little olive oil and spread with garlic sauce.