"Delicious dish with great flavor due to the browning of the gnocchi which gives it a crisp exterior. A quick tomato sauce is built in the empty skillet. The gnocchi goes back into the sauce and is finished with mozzarella under the broiler."
Adjust oven rack to upper-middle position and preheat oven to 475 degrees F (245 degrees C).
Heat 2 tablespoons oil in a large heatproof nonstick skillet over medium-high heat. Saute gnocchi until lightly browned, about 4 minutes. Transfer to a plate.
Heat the remaining oil in the same skillet. Add onion; cook and stir until onion is softened, about 3 minutes. Stir in garlic and red pepper flakes and cook until fragrant, about 30 seconds. Stir in tomatoes and water; cook until slightly thickened, about 5 minutes.
Place gnocchi back in the skillet; add basil. Reduce heat to low and simmer, stirring occasionally, until gnocchi is tender, 5 to 7 minutes. Sprinkle mozzarella cheese on top.
Transfer skillet to the preheated oven. Bake until cheese is well browned, about 8 minutes.