Combine flaxseed meal and 2 tbsp water in a small bowl and set aside for a couple minutes. Skip this step if using an egg.
Meanwhile, in another medium bowl, mix together all the dry ingredients.
Add the yogurt and oil to the flaxseed mixture (or egg) and stir to combine.
Start adding the yogurt mixture to the dry ingredients bit by bit, kneading the dough as you go. Then start adding warm water, bit by bit, as needed, making sure it is well absorbed before adding more. Depending on how watery your yogurt is, you may not need water at all.
Knead for a couple of minutes until the dough is well combined and soft. Cover and set aside for 15-20 minutes.
Now you will need to divide the dough into 6 balls. You can do this by rolling the dough into a log shape and then slicing it into 6 pieces. Or you can take pieces of dough and roll them into balls. Form the balls into a teardrop shape by rolling the bottom of the balls between your hands.
Heat a tava, griddle or non-stick (preferably cast iron) pan over high heat. Have butter/ghee and rice flour or other gluten-free flour nearby.
To shape the naan, use a combination of rolling out the dough with a rolling pin and gently pressing it with your hands. It should be around 5-6 inches long and 1/4 inch thick. Use a little rice flour or other gluten-free if the dough is sticky. Press in the edges gently to make them smoother.
Once you've rolled out the naan, sprinkle them with nigella seeds (kalonji) seeds and lightly press the seeds so that they stick to the dough.
Using a spatula, carefully lift the naan and place it on the hot skillet, seed side up. Add 1/4 tsp of butter or ghee to the top of the naan. After about 30-40 seconds, use your spatula to flip over the naan.
Once you’ve flipped the naan, cover it immediately with a lid large enough to cover the naan. Wait for 30-45 seconds and then remove it from the pan.
Brush with more butter or ghee, if desired. Cover with a cloth to keep warm while preparing the other naan. Serve hot.