01 -
Slice the green and red bell peppers along with the onion into thin strips.
02 -
Place sliced peppers and onions into a 4 to 6-quart slow cooker. Season with Italian seasoning, garlic powder, salt, and black pepper. Add marinara sauce and tomato paste, then stir until combined.
03 -
Cover and cook on low heat for 2 hours, stirring occasionally to ensure even cooking.
04 -
While vegetables cook, heat butter in a skillet over medium heat and brown the sausages on all sides until seared but not fully cooked.
05 -
Add the seared sausages to the slow cooker with the peppers and onions. Cover and cook on low for an additional 4 hours, stirring gently every hour to prevent breaking the sausages.
06 -
If desired, remove sausages, slice them, and return to the slow cooker before serving.
07 -
Serve hot by itself, on hot dog buns, or over pasta, rice, or noodles as preferred.