Single Recipe

Preheat

Preheat oven to 275°F (135°C).

Place halved tomatoes and sliced garlic in a small baking dish or rimmed sheet in a single layer.

Scatter thyme, salt, black pepper, and red pepper flakes over the tomatoes.

Pour the extra-virgin olive oil over the tomatoes so they are partly submerged in oil.

Bake low and slow for 45–60 minutes until tomatoes are softened, slightly collapsed and concentrated but not burnt. Remove from oven and let cool. Reserve oil for brushing bread or adding to the sandwich.

While tomatoes bake, heat olive oil and butter in a medium skillet over medium-low heat until butter melts.

Add the thinly sliced onion, sprinkle with kosher salt and the granulated sugar. Cook, stirring or tossing every few minutes, keeping the heat low to medium-low so onions soften and slowly brown. This should take 25–30 minutes.

If onions begin to stick, add a splash (1–2 tbs) of water or lower the heat. Continue cooking until deeply golden and sweet. Stir in apple cider vinegar and freshly ground black pepper, cook 1 more minute, then remove from heat and set aside.

Butter one side of each bread slice with the salted butter.

Optional: brush the unbuttered bread sides lightly with some reserved tomato confit oil for extra flavor.

Place one bread slice butter-side-down in a skillet or griddle over medium heat. On the unbuttered side, layer half of the grated cheddar, then a generous spoonful of caramelized onions evenly, then a few spoonfuls of tomato confit (including some of the softened tomato pieces, but not too much loose oil), then the arugula, and finish with the remaining cheddar. Top with the second slice of bread, butter-side-up.

Cook the sandwich 3–4 minutes on the first side until golden brown and cheese starts to melt. Carefully flip and cook another 3–4 minutes until the second side is golden and cheese is fully melted. Lower heat if the bread browns too quickly before cheese melts. Press gently with a spatula while cooking to help cheese bind.

Remove sandwich from skillet, let rest 1 minute, slice in half, and serve immediately. If desired, spoon a few extra confit tomatoes on the plate.