Spread the butter on one side of each of the four slices of bread. The Mr. is adamant that butter coverage must be even. Spread it clear to the edges. It's worth the extra .2 seconds.

Heat one skillet over medium high heat. Add oil and allow it to heat. Add onions and peppers to the skillet. Allow them to sit for 1-2 minutes without stirring to develop some char. Then stir and cook for an additional 3-5 minutes or until just soft.

Meanwhile, heat another skillet over medium heat. Place all the bread slices butter side down into the skillet. Place the cheese slices on top of two of the bread slices. Cook until bread is golden brown and cheese is melted, about 6-7 minutes.

Remove bread slices to plate. Place onions and peppers on top of melted cheese then cover with the other slice of grilled bread. Dig in!