Use ripe avocados only — they should give slightly when pressed near the stem. Scoop the flesh out and discard any brown spots near the skin.
Add avocado, Greek yogurt, garlic, lime juice, lime zest, cilantro, jalapeño if using, olive oil, cumin, salt, and pepper to a blender or food processor. Blend on high until completely smooth, scraping down the sides once halfway through.
Add water one tablespoon at a time with the blender running until you reach your preferred texture. 2 tablespoons for a thick dip, 3–4 for a sauce or dressing.
Taste the dip. Add more lime juice for brightness, more salt if flat, or more jalapeño for heat. The avocado should be the main flavor — garlic and cumin are supporting notes.
Transfer to a serving bowl. Drizzle with olive oil and scatter cilantro leaves on top. Serve immediately with chips, vegetables, or flatbread. If storing, press plastic wrap directly onto the surface before refrigerating.