Get Ready: Preheat your oven to 350°F (175°C) and lightly spray a 9x13 inch baking dish with nonstick spray.
Cook Noodles: Boil your egg noodles in a large pot of water until they're al dente (just tender, not mushy). Drain them well and rinse with cold water to stop cooking.
Brown Beef: In a large skillet over medium-high heat, cook the lean ground beef with the chopped onion and minced garlic. Stir often until the beef is no longer pink. Drain off any excess fat for a healthier dish.
Simmer Sauce: Reduce the heat to medium. Stir in the marinara sauce, half of the kosher salt (½ teaspoon), and half of the black pepper (½ teaspoon) with the beef. Let it gently simmer for a few minutes to blend the flavors, then remove from heat.
Mix Creamy Layer: In a medium bowl, combine the cottage cheese, sour cream, green onions, and the remaining salt and pepper. Stir until everything is well mixed.
Coat Noodles: Add the cooked and cooled egg noodles to the sour cream mixture and toss gently until they are all evenly coated.
Layer It Up - First Round: Spread half of the creamy noodle mixture evenly across the bottom of your prepared baking dish. Next, spoon half of the beef sauce over the noodles, then sprinkle with 2 cups of the shredded cheese (cheddar and Monterey Jack combined).
Layer It Up - Second Round: Repeat the layers! Add the remaining noodles, then the rest of the beef sauce, and finally top it with the remaining 1 cup of shredded cheese.
Bake to Perfection: Bake the casserole uncovered for about 30 minutes, or until the cheese is beautifully melted and bubbly around the edges. Let it rest for a few minutes before serving to ensure neat slices.