Heat the oven to 350° F. Butter the bottom and sides of an 8-inch, deep, fluted tart pan or an 8-inch round cake pan.
For the crumb, combine the dry ingredients in a small bowl. Using a fork or your fingers, gently work in the butter until pea-sized lumps are formed.
Combine the eggs, sugar, salt, and almond extract in a large bowl. Beat on high until the mixture triples in volume, about five minutes. Fold in the melted butter, flour, and rhubarb. Evenly spread the thick batter into the prepared pan. Sprinkle the crumb topping evenly over the top.
Bake for 60 to 75 minutes, until the topping is deeply golden and a toothpick inserted into the center comes out clean. Remove the cake from the pan when it’s completely cool.