Toaster-Oven Bacon and Onion Sliders | America's Test Kitchen

Ingredients

• 4 teaspoons mayonnaise
• 1½ teaspoons ketchup
• 1 teaspoon sweet pickle relish
• ⅛ teaspoon pepper
• 8½ ounces 85 percent lean ground beef
• ½ cup finely chopped onion
• 2 slices bacon , chopped fine
• 1½ teaspoons vegetable oil , divided
• ¼ teaspoon table salt , divided
• ⅛ teaspoon pepper , divided
• 4 (2½-inch) slider buns or soft dinner rolls
• 2 slices deli American cheese (2 ounces)