Cut the top off of the squash and a little of the bottom so it can stand. Scoop out the squash being careful not to cut through. Keep the good squash chunks that aren't seeds.
Brush the outside with olive oil and coat with salt.
Add the olive oil to a pan and sauté the sausage, garlic, onions, and peppers.
Add to the pan the rest of the ingredients and stir to combine. Cook for 2 minutes until the tomatoes and spinach are wilted.
Spoon the filling into the squash halves and top with cheese. Leave a little room at the top so the fillings don't overflow.
Bake for 30-35 minutes, until squash is tender and tops are golden.