Melt 2 tsp. butter in microwave, add flour and mix well.  Mix in milk until all lumps are gone.  Microwave for 2 minutes.  Chop cheese and add to milk mixture, stirring until smooth.  Microwave on high for 2 minutes until bubbly. In separate bowl, microwave onions in 2 tsp. butter until soft, about 2 minutes.  Mix peppers and cooked onion.  Add to cheese mixture.  Microwave on medium for 2 minutes more.