I begin by preheating the oven to 425°F (220°C). I wash, trim, and halve the radishes if needed. Then I toss them with olive oil, salt, pepper, and garlic powder until evenly coated.
I spread the radishes on a lined baking sheet in a single layer. They roast for about 20–25 minutes until golden and slightly caramelized. I flip them halfway for even browning.
While the radishes roast, I mix Greek yogurt, minced chives, garlic powder, salt, and pepper in a bowl. I stir until smooth and creamy. Then I set it aside until ready to serve.
If using butter, I melt it in a skillet over medium heat. I let it cook until it turns golden brown and smells nutty. Then I remove it immediately to prevent burning.
I spread the yogurt onto a serving platter. I arrange the roasted radishes on top and drizzle with brown butter. Finally, I finish with lemon zest and flaky salt.