4 tablespoons unsalted butter, cut into small cubes
1/4 cup slivered almonds
Preheat oven to 350°F. Line a standard size muffin tin with 12 liners and set aside.
In a large bowl, sift together both flours, baking powder, and salt. Set aside.
In a standing mixer with paddle attachment, whisk together butter, oil, eggs, and sugar until light and fluffy, about 2 minutes. Add in both extracts and mix well.
Turn speed to low and add in flour mixture and chopped rhubarb. Do not over mix.
In a separate bowl make the streusel. Combine the flour, brown sugar, and white sugar until completely combined. Add in the butter and use a pastry cutter to combine until the mixture resembles coarse sand. Add in the slivered almonds.
Pour batter evenly into the prepared muffin tin. Top each with a spoonful or two of streusel. Bake for 20 minutes, or until cakes are lightly brown on the top and a toothpick inserted into the middle comes out clean. Allow to cool and sprinkle with powdered sugar or enjoy as is!