A jar of kimchi in the fridge is a gateway to exciting, flavor-packed weeknight cooking. Here, kimchi, along with its brine, is used to quickly pickle tomatoes and zucchini. The salt and acid in the kimchi draws out the juice and sweetness from the tomatoes and tenderizes the vegetables. Since zucchini is close to 95 percent water, start by salting it briefly to draw out excess liquid and any bitterness, resulting in a texture that is creamy rat…