Break pasta into 1" pieces. Don’t worry if small pieces break off; cook them with the rest of the pasta. Combine ricotta and a pinch of salt and pepper in a small mixing bowl. Refrigerate until plating. Mince garlic.
Cook the Pasta
Once water is boiling, add pasta and cook until al dente, 11-12 minutes. Reserve 1 cup pasta water. Drain pasta in colander. While pasta boils, cook turkey.
Cook the Turkey
Heat a large oven-safe pan over medium-high heat. Add 1 tsp. olive oil and turkey to hot pan. Cook, stirring occasionally to break up meat, until no pink remains, 5-7 minutes.
Make the Sauce
Add Italian seasoning, garlic, and red pepper flakes (to taste) to pan with turkey. Cook, stirring constantly, until fragrant, 30-60 seconds. Add reserved pasta water and marinara to pan. Bring to a simmer. Cook, stirring occasionally, until sauce slightly thickens, 3-5 minutes.
Toss and Broil Pasta
Add pasta, spinach, and half the Parmesan to pan with sauce. Cook, stirring constantly, until spinach wilts, 1-2 minutes. Top with remaining Parmesan, and place pan under broiler until cheese is lightly brown and bubbles, 2-4 minutes.
Plate the Dish
Carefully, top lasagna with dollops of ricotta. Serve directly out of pan. Keep dish towel or oven mitt around handle to remind you the pan is hot!