California Sandwich

Name: California Sandwich
Ingredients: 1⁄4 cup buttermilk; 1⁄4 cup sour cream; 1⁄4 cup mayonnaise; 1 tbsp. finely chopped chives; 1 tbsp. finely chopped parsley; 1⁄2 tsp. garlic powder; 1⁄4 tsp. onion powder; Kosher salt and freshly ground black pepper, to taste; 4 slices multigrain sandwich bread; 2 slices Monterey Jack cheese; 1⁄2 cup alfalfa sprouts; 1 avocado, peeled, pitted, and thinly sliced lengthwise; 1 ripe tomato, cored and thinly sliced