Start with the potatoes. Preheat the oven to 400°F. Add the potatoes to a large baking dish and toss with the oregano, thyme, paprika, garlic powder, salt, pepper, lemon juice, olive oil and butter. Pour in about 1/2 cup of water to the bottom of the dish.
Bake for about 30–40 minutes, or until the potatoes are deeply golden and tender. If the water has completely evaporated halfway through cooking, add another small splash and continue baking. You want the potatoes to cook through while getting those crispy golden edges, flipping them halfway through.
While the potatoes cook, caramelize the onions. Melt the butter in a large pan over medium-low heat and add the sliced onions. Cook them low and slow, stirring occasionally, until they're soft, deeply golden and caramelized. This takes a little time, but it's worth it. Add more butter if the pan starts looking dry. If you want a little extra sweetness, stir in the brown sugar toward the end. Season with salt once they're finished.
This is where you can really use whatever you have on hand. Chicken, steak, kebabs or ground beef all work. I used ground beef from the butcher (because that's what I had on hand) and kept it in larger chunks rather than breaking it up too much. Heat a cast iron pan with a little olive oil, season the beef with salt and pepper, then cook until deeply browned, crispy and golden on the outside.
In a medium mixing bowl, mix together the Greek yogurt, grated and well-strained cucumber, lemon juice, garlic, dill, olive oil, salt and pepper. If your tzatziki is a little too loose from the lemon and cucumber, add cornstarch 1 teaspoon at a time, up to about 1 tablespoon, until it reaches the consistency you like.
In your serving bowls, start with a handful of lettuce on one side, then add the golden potatoes and meat alongside it. Add sliced tomatoes and cucumber, then tuck in a few big chunks of feta. Spoon a generous dollop of tzatziki right in the middle and scatter over fresh dill.
Finish the salad portion with a squeeze of lemon, a drizzle of olive oil, and a little salt and pepper. Then add those caramelized onions wherever they fit.
The best part is that there really isn't a wrong way to build this one. Crispy potatoes, salty feta, juicy meat, sweet caramelized onions and cool garlicky tzatziki all in one bowl.