In a large bowl, dissolve one tablespoon sugar and yeast into warm water. (Note: For the yeast to proof, the water must truly be lukewarm. Dip your finger in the water. If it’s too hot for your fingers, it’s too hot for the yeast as well. If it’s cool, it won’t work either.) Wait five to 10 minutes to allow the yeast to proof. It will appear foamy.

In a separate large bowl, or mixer fitted with dough hook, mix remaining cup of sugar, eggs, one cup oil, and salt. Mix in proofed yeast and spelt flour, four cups at a time, mixing until fully incorporated. Knead dough by hand or with the mixer until smooth and elastic, about five minutes. This dough will be sticky.

Drizzle remaining two teaspoons oil in a mixing bowl; roll dough in oil to coat. Cover with a towel and let rise until doubled, about one hour.

Grease six loaf or challah pans. Punch down dough. Divide into six pieces; divide each piece into at least three, and roll into long ropes about 12 inches long. Braid and place in prepared pans. Cover and let rise until doubled, about one hour.

Preheat oven to 350 degrees Fahrenheit.

Whisk egg yolk and water in a small dish. Gently brush on top of challah.

Bake for about 30 minutes, or until loaves are golden brown and bottom sounds hollow when tapped. Cool for 10 minutes in the pan, and then transfer challahs to wire racks.