Hjónabandssæla means “happy marriage” in Icelandic. Packed with sticky rhubarb jam and topped with oat crumble, this cheerful cake is an ode to wedded bliss.
Cream together 1/2 cup brown sugar and 1/2 cup margarine using an electric mixer until fluffy (around 1 minute on high speed).
To the creamed ingredients, add 1 ½ cup oats, 1 cup flour, 1 tsp baking powder, 1/2 tsp baking soda, and a pinch of salt. Mix on low speed to combine.
Transfer roughly two-thirds (350g) of the mixture to a square baking pan. (You can eyeball it; no need to be precise.) Gently press it into an even layer that covers the bottom of the pan.
Spread the 1/2 cup of rhubarb jam over top of the oat mixture.
Sprinkle the remaining oat mixture over to lightly cover the jam.