Portobello Burgers with Goat Cheese

Name: Portobello Burgers with Goat Cheese
Ingredients: 2 medium beets; 1/4 cup olive oil; 2 tablespoons balsamic vinegar; 1 teaspoon dried rosemary; 2 cloves garlic, minced and divided; 4 portobello mushroom caps; 1/2 cup goat cheese; 4 sandwich buns, split and toasted; 1 1/2 cups baby spinach leaves; 3 tablespoons mayonnaise; 2 cloves garlic, minced; 2 limes, juiced