Step 1

Preheat oven to 350°. Toast pistachios on a rimmed baking sheet, tossing once, until golden brown, 5–8 minutes. Let cool, then process in a food processor until very finely ground. Add garlic and lemon zest and process until a coarse paste forms. With motor running, stream in ¼ cup oil and process until mixture is smooth and no longer grainy (texture should be like tahini). Season with salt and pepper.

Step 2

Place yogurt in a medium bowl and season with salt and pepper. Thin with a little oil until about the same consistency as the pistachio paste. Fold pistachio paste into yogurt, leaving mixture marbled.