In a small bowl, combine shrimp, cumin, juice of lemon, and salt and toss to combine. Heat a skillet over medium high heat and add the butter to the pan. Once the butter is melted, add the shrimp to the pan and cook, stirring often, until the shrimp and pink and just cooked through, 2-3 minutes. Remove to a bowl to keep warm. Wipe the skillet clean, and warm each tortilla in the skillet according to package directions.
For slaw: In a large bowl, place the shredded cabbage and set aside. In a blender, blend together the remaining ingredients. Pour half of the dressing over the cabbage and mix well. Add more if needed or set aside the remaining dressing for extra sauce. Refrigerate for up to one week.
To serve, place a spoonful of slaw into each tortilla and top with 3-4 shrimp and a slice of avocado.