Apple Cheddar Quesadillas

Name: Apple-Cheddar Quesadillas
Ingredients: 5 tablespoons honey mustard, divided; 8 6-in. flour tortillas; 6 ounces sharp Cheddar cheese, shredded (about 1½ cups); 2 Honeycrisp apples, thinly sliced (2½ cups); 5 tablespoons olive oil, divided; 1 tablespoon plus 1 tsp. fresh lemon juice (from 1 lemon); ¼ teaspoon kosher salt; 1 5-oz. pkg. fresh baby spinach; 2 avocados, sliced (about 2 cups); ¼ cup roasted, salted pumpkin seeds (pepitas)