Preheat the oven to 400°F (200°C). Roll out the puff pastry on a lightly floured surface and cut into squares to fit your tart pans.

In a mixing bowl, whisk together the eggs, salt, and pepper. Stir in the cheese, spinach, and bell pepper until well combined.

Place the pastry squares into the tart pans and fill each with the egg mixture. Bake in the preheated oven for 20-25 minutes, or until the egg is set and the pastry is golden brown.

Allow to cool slightly before serving. Enjoy your breakfast tarts warm!