Heat the olive oil over medium heat in a pan large enough to fit all of the vegetables and sausage.
Add the sausage. You can squeeze it out of the casings directly onto the pan, or do this in advance in a clean bowl.
Break down bigger pieces with a spatula and cook for about 15 minutes, or until no longer pink inside.
When finished, transfer to a paper towel lined plate and set aside.
Add more olive oil, if needed, and add onions.
Toss and cook for a few minutes.
Add garlic and cook until aromatic.
Add bell peppers and sprinkle with sugar and salt. Mix well.
Cook, stirring occasionally for about 15 minutes, or until peppers are softened.
Add cooked Italian sausage, tomato sauce, and mix well. Cook for about 5 more miniutes over medium low heat.
Off heat, stir in spinach. Divide between the plates and sprinkle with freshly ground black pepper.
Enjoy!