Preheat oven to 400F and line a baking sheet with parchment paper.
Lay out puff pastry on a lightly floured surface. Cut into 4 squares. Using a knife, score a 1/2 inch border around each square, being careful not to cut all the way through the puff pastry. Prick the insides of the square with a fork. Brush the borders with the beaten egg.
In a bowl, mix ricotta cheese with spinach, dried basil and salt and pepper. Spread the mixture into the center of each square. Bake in the oven for 12 minutes.
Meanwhile, crack the 4 eggs into separate bowls so they are ready for a quick transfer on the tarts.
Remove tarts from oven and quickly sprinkle the diced tomatoes and red onion into each square, leaving a space in the center for the egg. Slide the egg into the center and return the tarts to the oven. Bake for an additional 12 minutes or until the eggs are set and the puff pastry is cooked.
Season tarts with salt and pepper and sprinkle with fresh basil. Serve.
Note: Metric ingredient measurements are provided as a courtesy using a third-party calculator and are rounded to the nearest unit. The recipes provided on this site have not been tested with metric measurements and their accuracy cannot be verified.
The nutritional information provided is based on third-party calculations and is an estimate only. Accurate nutritional facts will vary based on the particular brands used, portion sizes, measurement accuracy and more.