How to Make It
Preheat oven to 400°F. Thinly slice half of the cauliflower half (leaving core intact) and set aside remaining cauliflower half. Place cauliflower slices and raisins in a heat-safe bowl. Place water, 1/2 cup of the vinegar, 1 of the smashed garlic cloves, and ½ teaspoon of the salt in a saucepan and bring to a simmer over medium-high. Remove from heat and pour mixture over cauliflower and raisins in bowl and stir gently. Allow to pickle at room temperature at least 15 minutes or up to 30 minutes. Drain pickling liquid; discard or reserve for another use.
While cauliflower mixture pickles, cut remaining half of the cauliflower half into small florets and spread in an even layer on a rimmed baking sheet. Toss with 1 teaspoon of the oil and 1/8 teaspoon of the salt. Place in preheated oven and roast until cauliflower is tender and golden brown on the underside, 18 to 20 minutes, stirring halfway through cook time. Remove from oven.
Place almonds, roasted bell peppers, tomato paste, black pepper, crushed red pepper, and remaining 1 tablespoon vinegar, 1 smashed clove garlic, ½ teaspoon salt, and 2 tablespoons oil in a food processor and process until mostly smooth, about 1 minute, stopping to scrape down sides as needed.
Spread sauce evenly over toasted bread slices. Top with pickled cauliflower slices and roasted cauliflower florets. Garnish with parsley and crushed red pepper.