Bring a large pot of water to a boil and add the rice noodles. Cook according to package directions, typically around 5–7 minutes. Drain and rinse under cold water.

In a pot over medium heat, add cooking oil. Once shimmering, introduce the Tom Yum paste and sauté for about 1 minute until fragrant.

Pour in the broth while stirring to combine with the sautéed paste. Increase heat to bring to a gentle boil.

Add sliced mushrooms to the boiling broth and let simmer for 2-3 minutes. Then, add shrimp and quartered tomatoes, cooking until shrimp is pink.

Taste and adjust the flavors with fish sauce, lime juice, and brown sugar, stirring well.

Evenly divide cooked rice noodles into bowls. Ladle hot broth with shrimp and vegetables over the noodles.

Garnish with fresh cilantro, sliced Thai chili, and optional kaffir lime leaves. Squeeze fresh lime juice on top.