Preparation

Make the rempah:

• Cut all the dried chiles into 4 or 5 pieces each with scissors; shake out the seeds. Put the chiles in a small saucepan and cover with water. Bring to a boil and reduce the heat, simmering until the chiles are soft and flexible, about 3 minutes. Drain the chiles, reserving the water. Put the chiles in a blender.
• Trim off the root and top section of the lemongrass, leaving a 5- to 6-inch section of bottom stem. Remove the fibrous outer layers until you reach the tender white core. Smash this core with the side of a knife to flatten it slightly. Cut it in half lengthwise and then slice crosswise into thin pieces.
• Add the lemongrass, ginger, almonds, shallots, garlic, fish sauce, fresh chiles, and 3 tablespoons of the reserved chile water to the blender. Blend to a smooth purée, adding a few more tablespoons of the chile water, or up to 1/2 cup total if needed, to facilitate blending.

Cook the shrimp in the rempah:

• Heat a nonstick wok or stir-fry pan or a large sauté pan over medium heat for 2 minutes. Add the oil and swirl to coat the pan. Scrape the rempah into the pan and fry gently, stirring continuously with a wooden spoon until the oil and rempah are blended and emulsified, about 1 minute. Continue frying, stirring occasionally, until the mixture darkens and thickens to a porridge consistency, 3 to 5 minutes. (If you added extra water to the blender, it may take longer to thicken.) The rempah should separate, with reddish beads of oil on the surface.
• Increase the heat to medium-high and add the shrimp and onions. Fry them, tossing and flipping frequently, until the shrimp feel firm to the touch and the onions are crisp-tender, 3 to 5 minutes. Add the tomato, sugar, salt, and lime juice, stirring and cooking just long enough to mix and to heat the tomato wedges without breaking them apart.

Serve with steamed rice.