Ingredients

• 8 slices white sandwich bread
• 4 tablespoons unsalted butter, room temperature
• 1/2 small sweet onion, sliced into 1/8-inch-thick rounds
• Flaky sea salt
• Coarsely ground black pepper
• Chopped parsley (for serving)
• A 3 1/2-inch-diameter cookie cutter

Instructions

1. Using cutter, punch a round from each slice of bread. Spread both sides with butter and top 4 rounds with 2 onion slices each; season with salt and pepper. Close sandwiches.
2. Heat a large skillet, preferably nonstick, over medium-high and cook sandwiches until golden brown, about 2 minutes per side (onion will soften slightly). Top with parsley and more salt.