Picnic Burgers (AKA Bacon Cheeseburgers with Grilled Watermelon and Lemon-Chive Slaw)

Ingredients

• ½ cup mayonnaise
• 2 TBSP fresh lemon juice
• 2 tsp. freshly grated lemon zest
• 1 TBSP honey Dijon mustard
• 1 TBSP grainy Dijon mustard
• 2 tsp. sugar
• 1/3 cup minced fresh chives
• 1/8th tsp. sea salt
• 1/8th tsp. freshly ground pepper
• 4 cups angel hair coleslaw (finely shredded cabbage)
• ¾ cup grated red onion
• 1 TBSP minced fresh thyme
• 1½ TBSP Lea & Perrins Worcestershire Sauce
• 1½ TBSP double strength tomato paste
• 1½ tsp. kosher salt
• 2 tsp. freshly ground pepper
• 2 pounds ground chuck
• 12 slices thick-cut bacon
• 6 ½-inch thick slices seedless watermelon, cut into circles to fit buns
• vegetable oil for grill grates
• 6 thin slices medium-sharp cheddar cheese
• 6 crusty onion buns or Kaiser rolls