Over medium high heat, cover rice vermicelli with water in a large pot and boil until tender, about 10 minutes. Taste test to check. Strain and rinse well with cold water to remove starch. Set aside to continue straining.
1 package rice vermicelli
To make the soup, in a large pot over medium heat, cook the onions in chili and olive oils until translucent, about 2 minutes.
1 medium onion, 1 tsp chili oil, 1 tbsp olive oil
Meanwhile, mash tamarind paste into 1 cup water until almost all of the fruit is dissolved and only pulp remains. Strain the pulp and pour the tamarind slurry into the pot. Continue adding more water to dissolve the fruit. Add the remaining amount of water into the pot. Add salt and chili flakes and bring to a boil.
1 package tamarind paste, 7 cups water, 1 tsp salt, ¼ tsp dried chili flakes
Add the tofu, tomatoes, pineapple and the white part of the green onion and bring soup to a simmer. Let this stew for about 15 minutes. Serve over rice vermicelli and garnish with thinly sliced green onion.
1 block firm tofu, 3 small vine tomatoes, 1½ cup diced pineapple, 1 green onion