In a large bowl, whisk together the flours, salt, instant yeast, and caraway seeds if using. Add the lukewarm water, followed by the honey and olive oil. Using a spatula, stir to combine. Dough will be wet and sticky. Cover the bowl with a towel and set aside for 30 minutes.
Using wet hands, grab one side of the dough and pull it up and to the center — the dough may tear and it might feel very fragile. Repeat this several times re-wetting your hands as needed to prevent sticking or, if you are familiar, you can slap and fold the dough several times until it feels smoother and more elastic — the purpose of this step is simply to ensure the flour is completely absorbed by the water and also to help develop some gluten. Cover the bowl and set it aside in a warm place to rise until it doubles in volume, roughly 2 hours.
Heat the oven to 375ºF. Butter a 10x5-inch loaf pan generously with softened butter.
When dough has doubled, gently deflate it; then turn it out onto a floured work surface. Pat it into a rough rectangle, then roll it into a log. Transfer log to prepared loaf pan.
Let the dough rise until it crowns the rim of the pan, 45 minutes to an hour.
Transfer to the oven and bake for 45 minutes. Turn loaf out onto a cooling rack. Let cool for at least 20 minutes before slicing. Once completely cool, transfer to an airtight bag and store at room temperature for up to 3 days or freeze for up to 3 months.