Cook the spaghetti according to package instructions, drain and set aside.
While the spaghetti is cooking, trim and cut into pieces the peppers and the onion.
Place pepper and onion pieces in a food processor, along with garlic and bouillon cube. Pulse to break down the vegetables.
Add the sour cream, then process until the mixture is smooth.
In a large saucepan, melt the butter, then add the pepper mixture and bring to a simmer.
Season with salt and pepper, cook for about 4-5 minutes, then add the spaghetti and toss to coat.
Serve and enjoy!