For the Sourdough Pre-Starter (Make 2 Days Ahead):

1. In a glass jar, combine 1/2 cup rye flour, 1/2 cup warm water, and 1/8 teaspoon sugar. Mix thoroughly with a fork or rubber spatula until no dry flour spots remain.
2. Cover jar with cheesecloth or screen (not a sealed lid). Let sit at room temperature (70°F/21°C) for 2 days to gather natural airborne yeast. The mixture will bubble slightly and develop a yeasty aroma.

For the Bread:

1. In a stand mixer bowl, combine 1 cup bread flour, cocoa powder, 3 tablespoons sugar, salt, onion powder, caraway seeds, and yeast. Whisk to combine.
2. Add the sourdough pre-starter, lukewarm coffee, olive oil, and molasses to the flour mixture. Mix with paddle attachment on medium speed for 4-5 minutes until thoroughly combined.
3. Switch to dough hook attachment. Add 1 cup rye flour, then gradually add remaining rye flour and bread flour until dough forms and becomes firm (not sticky). Knead on medium speed for 5-7 minutes until smooth and elastic.
4. Place dough in a lightly oiled bowl and turn to grease the top. Cover with a clean kitchen towel. Let rise in a warm place (75-78°F) for about 1 hour or until doubled in size.
5. Turn dough onto a lightly floured surface and punch down to remove air bubbles. Shape into a round loaf.
6. Place shaped dough on a lightly greased cookie sheet or in an 8-inch layer cake pan. For best results, use a 5-quart cast iron Dutch oven with the lid prewarmed to 130°F/55°C. Cover and let rise in a warm place for 30-40 minutes.
7. Preheat oven to 400°F (205°C).
8. Using a sharp knife or bread lame, cut 3-5 parallel lines about 1/4 inch (6mm) deep across the top of the loaf to prevent splitting during baking.
9. Bake for 30-35 minutes until the internal temperature reaches 200-205°F and the crust is very dark brown. The bottom should sound hollow when tapped.
10. Remove from pan or Dutch oven immediately. Place on a cooling rack for at least 45 minutes before slicing.