In a large glass, dissolve the yeast and 1 teaspoon of sugar in ¾ cup of warm water (about 100 degrees F). Let it sit on your counter until frothy, about 10 minutes.
Meanwhile, sift the flour, salt, remaining 1 teaspoon of sugar, and baking powder into a large, deep bowl.
Once the yeast is frothy, add the yogurt and olive oil to the glass and stir to combine. Pour the yogurt mixture into the dry ingredients and gently mix with a fork. When the dough is about to come together, use your hands to mix. Stop kneading as soon as it comes together—the dough should feel a bit sticky.
Cover the dough with plastic wrap and let it sit in a warm, draft-free place for 3 hours.
After 3 hours, prepare 2 bowls: one with extra flour and one with water. The dough will still be sticky. Separate it into 6 equal portions and lightly roll each one in the flour to keep them from sticking to each other.
Using a rolling pin, roll each piece of dough into a circle about ¼ inch thick. Repeat this process with the remaining dough.
Warm a large cast-iron skillet over high heat until it's nearly smoking. Make sure you have a lid large enough to fit the skillet and a bowl of melted butter ready.
Dampen your hands in the bowl of water and pick up a piece of naan, flip-flopping it from one hand to the other to lightly dampen it. Gently lay it in the skillet and set a timer for 1 minute. The dough should start to bubble.
After about 1 minute, flip the naan. It should be blistered and somewhat blackened. Cover the skillet with the lid and cook for about 1 minute more.
Remove the naan from the skillet, brush generously with the garlic butter, and sprinkle with a little kosher salt. Place the naan in a tea towel-lined dish to keep warm. Repeat with the remaining naan and serve immediately.