1/4cup(57g)butter, at room temperature, salted or unsalted (if salted omit added salt below)
1/2largeegg, see Note 2
1/2teaspoonvanilla
1cup(125g)all-purpose flour
1/2cup(113ml)buttermilk, milk or soured milk, see Note 3 below
1/2teaspoonbaking soda
1/2teaspoonbaking powder
1/2teaspooncinnamon
Generous pinch of salt, omit if using salted butter
1 - 1 1/2cupsrhubarb, fresh or frozen, cut into 1/2-inch dice
Topping:
1/2teaspooncinnamon
1/4cup(45g)brown sugar
1/4cup(55ml)walnuts or pecans, chopped (can omit)
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Instructions
Preheat oven to 350F. (regular bake/not fan-assisted)
Prepare the topping mixture by stirring together the topping ingredients. Set aside.
In a medium bowl, whisk together the flour, baking soda, baking powder, cinnamon and salt, if using. Set aside.
In a bowl with an electric mixer or the bowl of a stand mixer fitted with a paddle attachment, beat together the white and brown sugar, butter, egg and vanilla. *If using frozen rhubarb, toss the rhubarb in 1 Tbsp of the flour mixture, adding the remainder of the flour mixture to the batter.
Add the flour mixture to the bowl, along with the buttermilk (or milk) and mix until completely blended.
Fold in rhubarb, then spoon the mixture into a greased 8x8-inch baking pan. Sprinkle the topping mixture evenly over the top of the batter.
Bake in preheated oven for about 30-40 minutes (for 8x8 cake), or until cake is golden, pulls away from the sides of the pan and tests clean when tested with a cake tester (be sure you are testing a batter area and not poking moist rhubarb). Frozen rhubarb/light pans will take the longest to bake. Fresh rhubarb/dark pans are the shortest. 9x13 cakes will take about 45 minutes.
Allow to cool 10-15 minutes before slicing, to enjoy warm or allow to cool completely, then tightly cover and store at room temperature.
Cake is best enjoyed on the day it's baked. As it sits longer, the cake starts to pick up moisture from the rhubarb. Cake can be frozen, though it should be enjoyed quickly, once thawed, to avoid an overly moist cake.
Notes
1. If you don't have any brown sugar on hand, simply replace it with the same amount of additional white sugar. Likewise, if you only have brown sugar on hand, use all brown sugar the same way. 2. To get 1/2 an egg, break the egg into a small cup and beat with a fork. Add 1/2 of that to the batter (just eyeball it) and refrigerate the remainder for another use. As it's only 1/2 an egg, you can probably go either up (add the whole egg) or down (omit the egg completely) without issue. 3. To make soured milk, add 1 1/2 tsp white vinegar or lemon juice to 1/2 cup of regular milk. Let stand for 10-15 minutes before using.Be sure to read the FAQ above the recipe card for more tips and ingredient substitution suggestions.