How to Make It
Preheat broiler to high.
Place tomatoes on a baking sheet. Broil tomatoes 15 minutes or until charred, turning once. Cool 5 minutes. Peel; discard skins.
Heat a large cast-iron skillet over medium heat. Add chiles and garlic. Toast chiles until smoke wisps appear (about 1 minute). Remove chiles from pan. Toast garlic 7 minutes or until well charred, turning occasionally. Remove from pan; cool 5 minutes. Remove garlic skins; discard.
Combine 2 cups water and achiote paste in a saucepan; bring to a boil, stirring until paste dissolves. Turn off heat. Add chiles; weigh down with a ramekin or saucer to keep submerged. Cover; let stand 45 minutes.
Combine tomatoes, chiles, garlic, 1/4 cup steeping liquid, salt, sugar, and vinegar in a blender; blend until smooth.