1/2 cup (2 ounces) crumbled blue cheese
1/4 cup canola mayonnaise
2 teaspoons chopped fresh thyme, divided
1/4 teaspoon hot pepper sauce (such as Tabasco)
1 pound lean ground sirloin
1 teaspoon freshly ground black pepper, divided
1/8 teaspoon kosher salt
1/2 teaspoon extra-virgin olive oil
4 (1/4-inch-thick) slices Vidalia or other sweet onion
2 teaspoons sherry vinegar
4 (1 1/2-ounce) 100% whole-wheat hamburger buns with sesame seeds, toasted
4 (1/4-inch-thick) slices tomato
2 cups loosely packed arugula
How to Make It
Preheat grill to medium-high heat.
Combine 1/2 cup blue cheese, mayonnaise, 1 teaspoon thyme, and hot pepper sauce in a small bowl; stir well.
Divide beef into 4 equal portions, shaping each portion into a 1/2-inch-thick patty. Sprinkle beef evenly with 1/2 teaspoon black pepper and salt.
Brush oil evenly over both sides of onion slices; sprinkle with remaining 1/2 teaspoon pepper. Place the patties and onions on grill rack coated with cooking spray; cover and grill for 3 minutes on each side. Set patties aside; keep warm. Place onion slices in a zip-top plastic bag; seal. Let stand 5 minutes; toss with remaining 1 teaspoon thyme and vinegar.
Spread cut sides of buns evenly with mayonnaise mixture. Arrange 1/2 cup arugula on bottom half of each bun; top with 1 patty, 1 onion slice, and bun top.