1 tsp. coriander seeds
1 tsp. black or brown mustard seeds
1/2 tsp. cumin seeds
2 cups white wine vinegar
Three 1/4-inch-thick slices peeled fresh ginger
One-half small yellow onion, thinly sliced lengthwise
1/2 cup sugar
2 tbsp. kosher salt
1 tsp. black peppercorns
1/2 tsp. ground turmeric
1/4 tsp. crushed red pepper flakes
One-half head cauliflower, cut into 1-1/2- to 2-inch florets
5 medium carrots, peeled and sliced 1/2 inch thick on the diagonal
One-half red bell pepper, cut into large dice
Put the coriander, mustard, and cumin seeds in a small saucepan. Toast the spices over medium heat, swirling the pan occasionally, until fragrant and slightly darkened, about 2 minutes. Add the vinegar, ginger, onion, sugar, salt, peppercorns, turmeric, red pepper flakes, and 1 cup water to the toasted spices. Bring to a boil.
Pack the cauliflower, carrots, and bell pepper in a 2-qt. heat-resistant glass bowl or measuring cup. Pour the hot brine over the vegetables. Let cool to room temperature and then cover and refrigerate for at least 2 and up to 14 days.