Preheat a grill pan to medium heat.
In a small bowl or ramekin, mash the avocado. Add the chopped sundried tomatoes with lemon juice, and mix until combined. Set aside.
Divide the meat into 4 piles, and form into patties by pressing them thin between your hands.
Place a heaping spoonful of the guacamole in the center of each patty. Fold the edges of the meat around the guacamole until it forms into a ball.
Gently pat the meat between your hands to flatten into a patty again. It’s fine if some guacamole comes out of the edges.
Place the patties on the preheated grill pan. Cook for
4–5 minutes, then flip the burgers and cook another
4–5 minutes on the other side until the burgers are browned on both sides.
Remove the burgers from the skillet. Serve immediately, and top with any leftover guacamole.