Heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Add garlic to pan; sauté 1 minute or until golden. Stir in broth, tomatoes, cumin, and beans; bring to a simmer. Cook 2 minutes, stirring occasionally. Remove from heat. Add spinach, tossing to combine.
Bring water to a boil in a medium saucepan. Add polenta, butter, and salt; stir well with a whisk. Reduce heat, and simmer 3 minutes or until thick, stirring constantly. Spoon 3/4 cup polenta into each of 4 bowls; top each with 3/4 cup bean mixture. Sprinkle 3 tablespoons cheese over each serving; garnish with black pepper, if desired.