Add the first eight ingredients to the saucepan and bring to a boil on the stovetop over high heat. Boil for 5 minutes.
Preheat the oven to 325°F (163°C).
Grease the two loaf pans or one tube (or bundt) pan and dust with rye flour. Set aside. (In my recipe video, I use one tube pan.)
While the mixture is boiling, place the flour, baking soda, and baking powder in a large mixing bowl and whisk together.
Remove the saucepan from the stovetop, place on a heatproof surface, and allow the mixture to cool.
Once the mixture has cooled, make a well in the flour and pour the wet mixture into the well. Mix together until the flour is completely incorporated and no streaks of flour can be seen. Do not over mix.
Divide the batter into two loaf pans or one tube (or bundt) pan. Smooth the top.
Place the pan(s) on the middle rack of the preheated oven and bake for approximately 1 hour or until a toothpick inserted into the cake comes out clean.
Using potholders, remove the pan(s) from the oven and let them cool on a heatproof surface for 10 minutes. Afterward, remove the cake from the pan(s), serve, dust with powdered sugar if desired, and enjoy!
Wrapped well, the cake can be stored in the refrigerator for three to four days or two months in the freezer.