Pomegranate Salsa with Pistachios

Bring vinegar to a boil in a small saucepan over medium-high; boil, swirling pan occasionally, until reduced by half, about 3 minutes. Remove from heat; set aside.

Brush both sides of onion slices evenly with 1 tablespoon oil. Heat a large cast-iron skillet over medium-high. Add onion, chile, thyme, salt, and black pepper; cook, undisturbed, until charred, about 3 minutes. Using a spatula, carefully flip onion rounds and chile. Cook, undisturbed, until charred on other side, about 3 minutes. Discard thyme.

Transfer onion and chile to a cutting board; let cool about 5 minutes. Chop onion into about 1/4-inch pieces. Remove and discard chile stem; finely chop chile. Place onion and chile in a large bowl. Add pomegranate arils, pistachios, chives, parsley, vinegar reduction, and remaining 3 tablespoons oil; stir to combine. Season with additional salt and black pepper to taste, if desired.