Melt butter in stockpot on medium heat. Sauté onion until clear, about 5 minutes. Add garlic and jalapeño peppers. Add zucchini and squash, sauté 2 – 3 minutes stirring continuously. Stir in frozen corn. Add tomato, stir to mix well. Add stock to bring to soupy consistency. Simmer 20 – 25 minutes. Serve with a splash of citrus juice and garnish with sour cream. Add salt and pepper to taste.