Preheat your oven to 375℉ (or 190℃) and grease a 9x9x2.5-inch square baking dish.

Add olive oil, diced onion, minced garlic, and a pinch of kosher salt to a deep-sided skillet. Heat on medium-low heat, stirring occasionally until softened—about 5 minutes.

Increase the heat to medium-high and add in your turkey sausage. Use a wooden spatula or spoon to break up the sausage as it cooks. Stir often until it's browned with no pink remaining. Once cooked through, drain any excess fat from the pan.

Pour in the marinara sauce directly into the skillet. Mix well and remove from heat.

In a medium bowl, combine ricotta cheese, egg, freshly grated parmesan cheese, and parsley. Season with kosher salt and black pepper before stirring until smooth.

Spread several large spoonfuls of sauce on the bottom of your prepared baking dish.