Heat oil in a heavy-bottomed pot over medium heat and add onion puree. Cook for 5-7 minutes until fragrant.
Add ginger, garlic, and chili purees. Stir constantly for 3-4 minutes until aromatic.
Stir in chili powder, turmeric, paprika, sugar, salt, and chopped tomato. Cook for 2-3 minutes.
Add pork cubes and water, then add lemongrass stalk.
Bring to a boil, then reduce heat and simmer for approximately 40 minutes until pork is tender and sauce has thickened.
Mix tamarind paste, soy sauce, and fish sauce together, then stir into curry.
Remove lemongrass stalk, garnish with cilantro and fried shallots, and serve with steamed rice.