There's nothing like coffee cake for breakfast. his recipe is is simple to make and is quite a filler. Makes one (9-in) round cake.
Preheat oven to 350 degrees F. Grease a 9-inch spring-form pan.
To make the cake, in a large mixing bowl, whisk the brown sugar with the olive oil and eggs until frothy.
Sift the flour, baking powder, baking soda, and salt over top, and fold in with a wooden spoon or spatula to form a soft batter. Add the milk and stir to combine. then fold in the rhubarb.
Pour the batter into the prepared cake pan. Tap the pan on the counter several times to ensure the batter is level and to remove any air bubbles.
To make the streusel topping , in a small bowl, combine the flour, oats, sugar, and zest. Drizzle in the olive oil and stir to combine into a coarse crumb mixture. Sprinkle this evenly over the cake batter.
Bake the cake for 35-40 minutes, or until a toothpick inserted in the center comes out clean. Remove from the oven , run a knife around the outside, and remove the sides of the pan.
Let rest for at least 10 minutes before serving.