1 tablespoon(s) extra-virgin olive oil
3 cup(s) thinly sliced Spanish onion
3/4 teaspoon(s) freshly ground pepper, divided
1/4 teaspoon(s) salt, divided
1 pound(s) lean ground pork
1 tablespoon(s) finely chopped Spanish green olives
2 teaspoon(s) minced garlic
2 teaspoon(s) Hungarian paprika
1/4 cup(s) reduced-fat mayonnaise
2 teaspoon(s) freshly grated lemon zest
1 tablespoon(s) lemon juice
1/4 cup(s) shredded Manchego or Monterey Jack cheese
4 whole-wheat hamburger buns, toasted
2 whole jarred Piquillo peppers, or jarred pimientos, halved lengthwise
Heat oil in a large skillet over medium heat. Add onion, 1/4 teaspoon pepper, and 1/8 teaspoon salt. Cover and cook, stirring occasionally, until soft and translucent, about 10 minutes. Set aside half the onion for topping; finely chop the other half.
Preheat grill to medium.
Place the chopped onion in a large bowl; add pork, olives, garlic, paprika, the remaining 1/2 teaspoon pepper, and 1/8 teaspoon salt. Gently combine, without overmixing, until evenly incorporated. Form into 4 equal patties, about 1/2 inch thick.
Combine mayonnaise, lemon zest, lemon juice, and saffron in a small bowl.
Oil the grill rack. Grill the burgers, turning once, until an instant-read thermometer inserted in the center registers 165 degrees F, 10 to 12 minutes total. Top with cheese and cook until it is melted, about 1 minute more.
Assemble the burgers on toasted buns with the lemon-saffron mayonnaise, some of the reserved onions and a half a Piquillo (or pimiento) pepper.