Generously butter two 8 or 9 inch cake pans

Combine the filling ingredients and set aside, stirring every few minutes - it will become very syrupy as the sugar melts and the rhubarb lets out its juice.

In a large mixing bowl, whisk together 1 & 1/4 cups of the flour, the yeast and salt.

Measure the milk, butter and honey into a 2 cup glass measure, or a small glass bowl, and microwave on low until the milk is warm - stir to melt the butter and get everything combined well. [this can be done on the stovetop, in a small pan, if you prefer]. You should be able to hold your finger in the mixture without feeling like it's burning you - if it is too hot, let it sit a few minutes before going to the next step.

Whisk the milk mixture into the flour mixture and whisk for a couple minutes, until the batter is very smooth.

Whisk in the egg.

Switch to a wooden spoon and mix in the final cup of flour, until well combined and the batter is fairly smooth.

Divide the batter between the two buttered 8 or 9 inch cake pans and spread to the edge - you can dampen your fingers to do this, or use a silicone spatula. I use a scale to get an equal amount in each pan.

Divide the rhubarb mixture evenly between the pans, getting it spread evenly over the cake layer.

Use a pastry cutter or a fork to blend the topping ingredients together - it will be a rather crumbly texture.

Spread the topping evenly over the rhubarb layer.

Set in a warmish place to rise for an hour.

Preheat oven to 350º, and bake the cakes for around 40 minutes.

Use a toothpick to test that the cake layer is done - there should be no crumbs on it at all. The fruit layer should be bubbly, and the topping nicely browned.

Cool in pans on a rack.

The cake can be served from the pan, or you can put it on a plate by loosening around the edge with an offset spatula, and then kind of keeping the spatula under the cake as you guide it onto a plate. Serve warm or at room temperature. You can top it with a bit of glaze [1 cup confectionery sugar with cream mixed in to give it a drizzle-able consistency], whipped cream, vanilla ice cream, creme fraiche, Greek yogurt - or just eat it plain.

Store leftovers in the fridge or wrap tightly and freeze to keep longer than a few days.