01 -
Slice the green and red bell peppers along with the onion into thin strips.
02 -
Place the sliced peppers and onions into a 4 to 6-quart slow cooker. Add Italian seasoning, garlic powder, salt, and pepper. Pour marinara sauce and tomato paste over the vegetables and stir to combine.
03 -
Cover and cook on low heat for 2 hours, stirring occasionally until the peppers and onions soften.
04 -
Meanwhile, heat butter in a skillet over medium heat. Brown the Italian sausages on all sides, approximately 5 to 7 minutes. This step is optional but adds flavor.
05 -
Add the browned sausages to the slow cooker with the vegetables. Cook on low for an additional 4 hours, stirring every hour gently to avoid breaking the sausages.
06 -
If desired, remove sausages, slice them, and return to the slow cooker. Serve warm, either on their own, in sandwiches, or over pasta.