Warm the olive oil in an oven-safe skillet over medium-high heat. Add the ground beef, celery, onion, and minced garlic. Break up the meat and cook until it's no longer pink, which usually takes about 5 to 6 minutes.
Stir in the marinara sauce, salt, and pepper with the browned meat. Reduce the heat to low and let it gently simmer while you get the cheesy layer ready.
In a roomy bowl, combine the ricotta (or cottage cheese), half of the mozzarella, all the Parmesan, the beaten eggs, Italian seasoning, minced garlic, garlic powder, and pepper. Mix everything well until it's smooth and combined.
Carefully spread the delicious cheese mixture evenly over the simmering meat layer in the skillet. Then, sprinkle the remaining mozzarella cheese on top. Cover the skillet and let it cook on medium-low heat for 10 to 15 minutes, until the cheese layer is hot and set.
While the lasagna is cooking, preheat your broiler. Once the cheese layer is set, transfer the skillet to the broiler. Broil for 2 to 3 minutes, or until the cheese on top is bubbly and beautifully golden brown. Keep a close eye on it to prevent burning!
Let your skillet lasagna rest for about 10 minutes before serving. This helps it set further, making it easier to scoop and enjoy!