Created by ForeverMama on September 15, 2016
Step 1: In a 3 - 4 quart pan, combine the Madeira or port wine, vinegar, sugar, currants, and cayenne. Boil rapidly, uncovered, until reduced to 1 1/4 cups; set aside.
Step 2: Peel onions, arrange a single layer of onions in a 12 - 14-inch frying pan (reserve extra onions to cook in sequence). Add oil. Cook over medium-high heat until lightly browned, about 7 minutes, shaking pan to turn onions.
Step 3: With a slotted spoon, transfer browned onions to pan with Madeira sauce. Brown remaining onions in frying pan, then add to sauce.
Step 4: Bring onions and sauce to a boil. Reduce heat, cover, and simmer gently; allow 10 minutes for small onions, 15 minutes for larger ones. Onions will be slightly crisp inside. Let cool; season to taste with salt.
Step 5: If made ahead, cover and refrigerate for up to 4 days; serve at room temperature.