Cheeseburger with Grilled Onions

Ingredients

• 1 lb of 90/10 lean ground beef
• 1 tbsp of Olive Oil Divine's Austin Steakhouse Rub
• 3 tbsp of Olive Oil Divine's Butter Flavored Extra Virgin Olive Oil, divided
• 1 medium yellow onion slice
• 4 pieces of leaf lettuce
• 4 slices of ripe tomato
• 4 slices of American cheese (or cheese of your choice)
• 4 whole wheat buns
• 2 tbsp of Olive Oil Divine's Cask 25 Aged Dark Balsamic Vinegar