Preheat oven to 375 degrees F (190 degrees C). Line a baking sheet with foil.
Place Cherry Tomato (1 cup) and Red Onion (1) on baking sheet and drizzle with a few swirls of Olive Oil (to taste), Salt and Pepper (to taste).
Bake for about 30 minutes, until a bit charred and soft.
In a bowl, mix Ricotta Cheese (2 cup) with Egg (2), Salt (1/2 teaspoon), Ground Black Pepper (1/2 teaspoon), and Parmesan Cheese (1/3 cup). Mix well with a hand beater or wooden spoon.
Add All-Purpose Flour (1/2 cup) and mix well again.
Add Unsalted Butter (2 tablespoon) and Whole Nutmeg (to taste).
Transfer to a glass 9-inch round dish, spread evenly and bake for 45 minutes, until light brown on top. Let cool on a wire rack.
Mound tomatoes and onions on top of the ricotta, then scatter Arugula (1 cup) and Shaved Parmesan Cheese (to taste).
Drizzle with olive oil, some salt and pepper, and serve cut into wedges.