Heat a drizzle of oil in a medium pot over medium-high heat. Add tomato and remaining garlic. Cook, stirring, until softened, 1-2 minutes. Add beans, ½ cup water (⅓ cup for 4), stock concentrate, 1 tsp Southwest Spice (1 TBSP for 4), salt, and pepper. Simmer until thickened, 5-10 minutes. Turn off heat; stir in 1 TBSP butter (2 TBSP for 4). Season with salt and pepper. Keep covered off heat until ready to serve.