Add all of the ingredients for the watermelon salsa to a large bowl. Stir to combine.
Place the salsa in the refrigerator.
Cook the chorizo in a skillet on the stove over medium high heat for 8-10 minutes, or until cooked through.
Place the chorizo on the tostada shells, then top with the watermelon salsa and queso fresco.
To make the avocado cream sauce, puree the avocado, lime juice and cilantro in a blender or food processor and drizzle over the tostadas.
Notes
Vegetarian Option: Use soyrizo to make this recipe vegetarian. Omit the queso fresco to make it vegan.
Gluten Free Option: This recipe is gluten-free when gluten-free chorizo is used. Brands vary, so be sure to check labels to find a chorizo that is gluten-free.