1-First Step: Prep Your Pan and Oven Preheat oven to 350F. Grease an 8-inch square pan. Line with parchment paper for easy release. This setup prevents sticking. Let zucchini sit out if cold for even mixing. Takes 2 minutes max.

2-Second Step: Shred and Whisk Wet Ingredients Shred 2 1/4 cups (237g) zucchini as thin as possible without breaking strands. Include all water, do not drain or pat dry. In a large bowl, whisk zucchini, 1 1/2 cups (295g) sugar, and 6 tbsp (84g) melted unsalted butter. Whisk until sugar dissolves a bit, about 1 minute. Batter looks wet and uniform.

3-Third Step: Fold in Flour Add 2 1/2 cups + 2 tbsp (339g) self-rising flour. Fold gently with spatula until no dry pockets remain. Batter stays thick, like muffin batter. Avoid overmixing to keep it tender. If no self-rising flour, make homemade: mix 3 cups all-purpose flour, 4.5 tsp baking powder, 0.75 tsp salt.

4-Fourth Step: Spread and Bake Spoon thick batter into prepared pan. Spread even with spatula. Bake at 350F for 40-50 minutes. Check at 40 minutes; toothpick comes out clean when done. Edges pull from pan sides.

5-Final Step: Cool and Serve Cool cake fully in pan on rack, at least 1 hour. Lift out with parchment. Slice into 12. Frost if desired: Beat 1/2 cup softened butter, 8oz softened cream cheese, 1 tsp vanilla, 3-4 cups powdered sugar until creamy. Spread thick layer, garnish with pistachios.