Place flour, sugar (if using honey add it later along with the eggs), yeast, and salt in the bowl of a standing mixer fitted with the dough hook and mix on until combined. Add eggs, water, and butter, and mix on low-medium speed for 10-12 minutes until the dough is smooth and elastic. It would look soft and won’t pull away from the bottom of the bowl - that’s ok. During mixing, scrape down the sides of the bowl using a spatula as needed.
In a medium bowl, whisk together butter, sugar and cinnamon until well combined. It should be a thick spreadable consistency.
Carefully lift the cake into a loaf pan. Don’t worry if the cake doesn’t look great or if there are gaps in the pan since the cake will rise and look fine, even if it looks messy at this point. Cover the pan loosely with plastic wrap and leave to rise at room temperature for 1 to 1½ hours until almost doubled in size. Repeat using the remaining dough and filling to create the second cake.
Preheat oven to 350ºF/175ºC, making sure to allow plenty of time for it to heat fully before the cakes have finished rising. Remove plastic wrap and place cakes on the middle rack of the oven. Bake for about 35-40 minutes until golden brown on top. If you have a thermometer, you are looking for an internal temperature of about 200ºF/93ºC degrees.
Babka will stay fresh for 24 hours in an airtight container at room temperature. Do not place it in the fridge. It also freezes well for up to 2 months. To thaw, leave at room temperature for 2 hours, or overnight in the fridge.