Soften the butter at room temperature.
Lay out two slices of bread.
Spread butter on one side of each slice all the way to the edges.
Place one slice butter-side down in a cold pan.
Add cheese slices on top of the bread.
Place second slice on top with butter-side up.
Turn heat to medium-low.
Cook for 3 to 4 minutes until the bottom is golden brown.
Flip carefully with a spatula. Press down gently.
Cook the other side for 3 to 4 minutes until golden.
Remove from pan. Let rest for 1 minute.
Cut diagonally and serve hot.