Pat salmon dry and season with salt and pepper. Place Dutch Oven over medium-high heat and add oil.

Sear fish on both sides until golden brown. Transfer to a plate and let rest.

Add garlic, shallots, and scallion whites to the Dutch Oven. Sweat aromatics until fragrant, 3–5 minutes.

Add tomatoes, stock, fish sauce, and sugar, and increase heat to medium-high. Use a Wooden Spoon to break up the tomatoes.

When the mixture comes to a boil, return the seared salmon to the pan and cover with lid. Reduce heat to low and cook until the fish is tender, about 15 minutes.

Season with salt and a generous amount of black pepper. Top with Thai chiles and reserved scallion greens.