I do love bread and carbohydrates, specifically whole wheat versions since they have a lower glycemic load than refined flour products (and I believe they can, and should, be part of a well-rounded diet). However, if you're looking to swap out the bread in this particular meal, or go for a gluten free option that's not a GF bread, a few good options would be corn tortillas, cauliflower tortillas, or a fun twist could be turning this sandwich into a breakfast bowl by starting with some black beans, layering sautéed veggies, chopped deli meat/bacon/sausage, cooked egg, and topping off with the avocado pesto!