Prep the cauliflower by breaking up the whole cauliflower and cutting off the florets. Wash the florets off and pat dry.
Preheat the oven to 425 degrees.
Place the cauliflower florets in a large mixing bowl. Drizzle with the olive oil and sprinkle the garlic powder, salt and black pepper over the cauliflower.
Spread the cauliflower in a single layer on baking sheet. You can line the baking sheet with parchment if desired. Bake for 25-30 minutes, mixing once halfway through cooking, until the cauliflower is softened and has become golden brown. Remove from oven and cool for 5 minutes.
Combine Greek yogurt, mayonnaise, lemon juice, minced fresh garlic, dried dill, oregano, salt, black pepper and in a small bowl and stir to combine.
Drizzle the cauliflower with the yogurt sauce and top with crumbled feta and chopped fresh dill and mint before serving.