Even though this recipe is pretty straightforward, you could add red pepper flakes, black pepper, and cayenne pepper to the dish. The good news is that if you don't want to add any spice to the dish as a whole, any of those options could be added to each person's individual serving as well. If I'm ever looking at adding spice or heat to a recipe, I tend to try and do that individually because most people don't care for foods that are overly hot and spicy.