Put chopped kale and sliced fennel in a large bowl.
Place pistachios on a foil-covered baking sheet and lightly toast. You can either do this in a toaster oven or by roasting at 350 degrees for about 6 minutes. Keep a close eye on them to make sure they don't burn.
Put pistachios in a blender (reserve a few for topping your salad), along with the garlic, lemon juice, hot water, about ⅓ cup extra-virgin olive oil, salt, and pepper.
Blend well, until the mixture is smooth. If you want a thinner dressing, continue to slowly pour in olive oil and blend. Taste. Add more salt and pepper if needed.
Toss kale and fennel with dressing until very well coated.
Serve salad on plates and top with extra pistachios, red pepper flakes, and lemon zest.