Filipino Sour Soup

Name: Filipino Sour Soup
Cuisine: Asian
Ingredients: 500g pork belly or ribs (cut into bite sized pieces); 1 medium onion, quartered; 2 medium tomatoes, quartered; 6 cups water; 1 packet tamarind soup base mix (or ½ cup fresh tamarind pulp); 2 tbsp fish sauce; 1 tbsp cooking oil; 1 medium radish (daikon), sliced thinly; 1 cup long beans (sitaw), cut into 2-inch pieces; 1 cup eggplant, sliced into rounds; 1 bunch water spinach (kangkong) or spinach, washed and trimmed; 2 green chili peppers (siling haba), optional; Fish sauce with sliced chili (optional)