In a small microwave-safe bowl, warm the water in the microwave for about 1 minute. (It should be warm but not hot to the touch; if you have a food thermometer, it should register 105 to 110 degrees F.) Sprinkle in 1 teaspoon of the sugar and swirl it around so it dissolves. Lightly sprinkle the yeast into the sugar water and allow the yeast to awaken for 7 minutes.
In another small microwave-safe bowl, heat the coconut oil in the microwave for 30 seconds or just long enough to bring it to a liquid state. Set aside.
In a large bowl, combine 2 cups of the flour with the remaining 1⁄2 cup of sugar, baking powder, salt, and turmeric and mix with a fork.
Add the yeast mixture and melted coconut oil to the dry ingredient mixture and stir until combined. Slowly add the remaining 2 cups of flour and, using your hands, knead the dough for a full 10 minutes, until all the flour is incorporated and you have a smooth dough.
Grease a large bowl. Place the dough ball in the bowl, cover loosely with a damp towel, place in a warm area (such as near the oven or in the sun), and allow to rise for about 1 1⁄2 hours.
After the time has passed, very lightly flour a flat surface and roll your risen dough into a long, thick snake 14 to 16 inches long. To make a classic three- strand braid, cut the dough into equal thirds. Starting in the center of the dough piece and using your hands to gently roll outward, roll each piece into a strand that is 12 to 14 inches long with the ends slightly tapered. Once all three dough pieces are rolled out, bring one end of each strand together and massage them firmly together to stick. Just as in a traditional braid, bring the left strand over the center one, making the left strand the new center strand. Then bring the right strand over the center strand, making that the new center strand. Repeat this pattern (left to center, right to center, and so on) until you reach the end of your strands. Press the ends together and tuck them under the end of your loaf. Go back and tuck the top of the loaf as well to produce rounded ends.
Line a baking sheet with parchment paper or a silicone mat. Place your loaf on the baking sheet, cover with a damp towel, and allow to rise for another 50 minutes.
Preheat the oven to 350 degrees F.
Once your loaf is looking nice and puffy, remove the cloth. Using a basting brush, lightly spread the agave evenly across the entire loaf, including the sides. Sprinkle the loaf with the sesame or poppy seeds. Bake for 35 to 40 minutes, until the top is hardened and a rich golden brown.
Allow to fully cool before wrapping with a challah cover or towel. Tear (or slice) and enjoy!