Bring a large pot of salted water to a boil. Add the gnocchi and cook according to package instructions, usually about 2-3 minutes or until they float to the surface. Use a slotted spoon to transfer the gnocchi to a plate and set aside. Do not overcook them as they can get mushy.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and cook for about 3-4 minutes, stirring occasionally, until softened and translucent. Add the minced garlic and cook for another 30 seconds until fragrant but not browned.
Pour in the canned diced tomatoes with their juices. Stir in the Italian seasoning, then season with salt and pepper to taste. Let this simmer for about 5 minutes so the flavors meld and the sauce slightly thickens.
Reduce the heat to low and slowly stir in the heavy cream. Allow the sauce to heat through for another 3-4 minutes, stirring occasionally. The sauce will become creamy, luscious, and beautifully pink in color.
Add the cooked gnocchi to the skillet and gently toss to coat each piece in the tomato-cream sauce. Let it all warm together for 1-2 minutes so the gnocchi absorb a bit of that flavor.
Remove the skillet from heat. Garnish with fresh basil leaves and a generous sprinkle of grated Parmesan cheese. Serve immediately and enjoy the comforting goodness!