Bring a large pot of salted water to a boil. Add pasta and cook according to package directions until al dente. Reserve 1 cup pasta water, then drain.

While pasta cooks, heat a large skillet over medium-high heat. Add ground beef and cook, breaking it apart with a spoon, until browned and cooked through, about 6–8 minutes. Drain excess fat if needed. Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper.

In the same skillet, melt butter over medium heat. Add minced garlic and cook, stirring often, until the butter turns golden brown and smells nutty, about 3–4 minutes. Watch carefully so it doesn't burn.

Pour the lemon juice into the browned butter. Add cooked pasta and beef back to the skillet, tossing gently. Add 1/2 cup reserved pasta water and stir until a light sauce forms, adding more pasta water if needed for silky consistency.

Divide among bowls. Top each with parmesan, chopped parsley, a pinch of red pepper flakes, and a crack of black pepper. Serve immediately.