Prepare the tzatziki sauce. Stick it in the refrigerator to chill until the nachos are ready to serve.
Prepare the lamb: Heat a medium skillet with 1 Tbsp olive oil on medium-low heat. Once it’s hot, add the chopped onion and sauté for about 5-6 minutes, until the onions begin to soften.
Add the lamb to the skillet, breaking up with a wooden spoon. Season with the garlic powder, oregano, sea salt, and lemon zest. Cook for about 6-8 minutes, until the lamb is no longer pink. Set aside and allow to slightly cool.
Get out a large serving dish or cookie sheet for the nachos. Pull out your toppings, and layer in any way you like: the lettuce, cherry tomatoes, cucumber, olives, capers, and lamb.