Preheat and prepare pan. Position a rack in the center of your oven and preheat the oven to 350°F (177°C). Spray a 9”x5” loaf pan with cooking spray, or line with parchment paper and then spray with cooking spray.
Combine dry ingredients. In a mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, baking soda and salt. Set aside.
Combine wet ingredients. In a second mixing bowl, whisk together egg ,buttermilk, oil and almond extract.
Combine wet and dry ingredients. Add the dry ingredients to the wet ingredients and mix together with a spatula or wooden spoon just until just combined. Fold in chopped pistachios. Stir in food coloring if using. Do not overmix.
Bake. Spoon batter into prepared loaf pan. Bake in a preheated 350℉ (177℃) oven for 50-60 minutes until a toothpick inserted into the middle of bread comes out clean or with a few moist crumbs clinging to it (no wet batter) and top springs back to the touch when lightly touched. Remove from the oven and cool completely in the pan on a wire cooling rack.
Make glaze. In a small bowl, stir together the powdered sugar, milk, and almond extract. If glaze is too thick, add an additional tablespoon of milk. If glaze is too thin, add additional powdered sugar.