In a large skillet, melt the butter over medium heat. Add the Brussels Sprouts, chopped onion, and minced garlic. Cook until the Brussels Sprouts are browned and the onion is translucent, about 5 minutes. Season with salt and pepper, stirring well.
Add the gnocchi and water to the skillet. Continue cooking, stirring frequently, until the gnocchi begins to brown, about 7-10 minutes. Be sure to keep stirring to prevent the gnocchi from sticking to the skillet.
Stir in the lemon juice and cherry tomatoes, coating everything evenly. Serve in bowls with a sprinkle of Parmesan cheese on top, if desired. Enjoy!