For each sandwich:
2 slices whole grain bread
1 to 2 Tbsp. sautéed onion
1 to 2 Tbsp. roasted or sautéed red pepper
2 Tbsp. grated cheese
Heat a non-stick skillet. Add a little olive oil and the sautéed onions and peppers Sauté until fragrant. Scoop out of pan onto a slice of bread; return bread to skillet. Sprinkle grated cheese thickly over vegetables and top with second slice of bread. Cook until bread is toasted to your liking; flip and grill second side. Remove from pan. If you like, split the sandwich open and add mustard.
Sautéed onions: Thinly slice an onion (preferably sweet, but yellow is nice too). Sauté in a little olive oil over low heat until limp and golden.
Sautéed peppers: Wash pepper. Remove stem, seeds and ribs. Slice thinly and sauté in a little olive oil over low heat until limp and even slightly black in spots. Roasted peppers are available in a jar.
Both sautéed onions and peppers keep well in a tightly closed container in the refrigerator for up to 5 days.