Prepare Spicy Seasoning Mix. Store in airtight container. Shake before using to blend. Makes 3 tablespoons.
Shape ground beef into four 3/4-inch-thick patties. Press Spicy Seasoning Mix evenly into both sides of each patty.
Heat large heavy nonstick skillet 5 minutes over medium heat until hot. Add patties to skillet. Cook 12 to 15 minutes to medium doneness (160 degrees) or until centers are no longer pink and juices show no pink color; turn once.
Line bottom of each bun with lettuce and tomato; top with burger. Spoon ranch dressing evenly over burgers; sprinkle with onions.