In a large stovetop pan or skillet, heat oil over medium heat and sear sliced chicken sausage and diced onion until caramelized.
Add minced garlic and cook for 1-2 additional minutes.
Reduce heat to low and promptly add halved cherry tomatoes, tortellini, and water as well as salts and peppers. Gently stir to combine, scraping bits off the bottom of the pan.
Cover and let simmer for 5-7 minutes.
Remove lid to add fresh spinach and gently fold into pasta. Allow spinach to wilt within warm pasta on low heat, cover for an additional 1-2 minutes.
Serve warm with french baguette or crunchy garlic bread.