Form the meat into four 8-ounce burgers; brush with olive oil and season with salt and pepper on both sides. Grill the burgers until golden brown on each side and cooked completely through, about 5 minutes per side. Add cheese for the last minute of cooking. Place the burgers on the bun bottoms, add the tomato slice and top with large dollop of avocado relish. Cover with the bun tops and serve immediately.