The deli roast beef cries out for crispy bread and sweet onions, a classic combination that turns lunch meat into dinner. Caramelizing the onions takes time but very little of your attention, so you can rest while they cook down into jammy, deep flavor that elevates the simple sandwich.

Serves 2. 45 minutes, 10 at the stove.

About 540 calories a serving, 34 g protein, 19 g carbohydrate, 37 g fat. From USDA figures for 100% of the ingredients; amounts are the recipe's.

Cook mode

1. Slice 1 large onion into thin half-moons and melt 2 tablespoons butter in a skillet over medium heat. Add the onions with 1/4 teaspoon salt and stir to coat; let them begin to soften while you heat the bread.
2. Cut 2 pieces of crusty bread or split 2 rolls and place them cut-side up on a baking sheet. Toast under the broiler until lightly golden, about 2 minutes, while watching the onions; when the onions are soft and beginning to brown at the edges, lower the heat to medium-low and leave them to caramelize undisturbed for 20 to 25 minutes.
3. After 20 to 25 minutes, when the onions are deeply golden and soft, taste and adjust salt and pepper. Stir once and cook for another 5 minutes if they are still very wet, or transfer them to a bowl.25 min
4. Layer 6 oz [170 g] of the roast beef on each toasted bread piece, top with 1 slice sharp cheddar or 1.5 tablespoons horseradish cream, then pile the warm caramelized onions over the top. Serve at once.

Note Swap the cheddar for Swiss or provolone, or skip cheese altogether and use horseradish cream. The onions keep in the fridge for three days and warm gently in a pan with a splash of water. Serve with a sharp mustard, pickled vegetables, or a green salad dressed simply with vinegar and oil.