If using active dry yeast, dissolve it in the warm water with a pinch of sugar. Let it sit for about 5-10 minutes, or until frothy.
In a large bowl, combine the rye flour, all-purpose flour, and salt. Stir in the caraway seeds if using.
Make a well in the center of the dry ingredients. Add the sourdough starter (or activated yeast mixture), molasses, and vegetable oil. Mix until a dough forms.
Turn the dough out onto a floured surface and knead for about 5-7 minutes, or until smooth and elastic.
Place the dough in a lightly greased bowl, cover with a clean kitchen towel, and let it rise in a warm place for about 1-1.5 hours, or until doubled in size.
Preheat your oven to 375°F (190°C). Grease a loaf pan or line it with parchment paper.
Punch down the risen dough and shape it into a loaf. Place the loaf into the prepared pan.
Cover the pan with a kitchen towel and let the dough rise for an additional 30-45 minutes, or until it has risen slightly above the rim of the pan.
Bake in the preheated oven for 30-35 minutes, or until the bread sounds hollow when tapped on the bottom and is a deep brown color.
Allow the bread to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.
Slice and serve as desired. Rye bread is great with butter, cheese, or as a base for sandwiches.
Enjoy your meal!