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["To make the cake:", "Preheat oven to 350 degrees. Butter a 10-inch round springform cake pan, line bottom with a round of parchment paper, and butter the paper. Flour the greased pan. Mix flour and baking powder in a small bowl and set aside. In a standing mixer or using a hand mixer, cream butter, sugar, salt, and lemon zest at medium-high speed until fluffy. Beat in vanilla. Add eggs one at a time. Beat until eggs are completely mixed in. The mixture will appear broken; don't worry. Gradually add flour mixture and beat until flour is partially mixed in. Then stir by hand with a rubber spatula until all flour pockets are mixed in. The batter will be very thick at this point. Carefully add the blueberries and spread throughout the mixture with a gentle folding motion. Avoid squashing the berries. With a rubber spatula spread the mixture into the prepared pan, pushing the thick batter to the edges of the pan and smoothing out the top as much as possible.", "", "To make the streusel:", "In a food processor, combine flour, brown and white sugar, cinnamon, and salt and pulse a few times until ingredients are combined. Add butter and pulse until the butter is evenly distributed, however the mixture does not need to be completely homogenous. Do not over-process; you want the mixture to seem sandy, not pasty.", "", "To assemble and bake the cake:", "Gather handfuls of the streusel and sprinkle clumps all over the top of the cake. If the streusel mixture is too fine, squeeze it together in your hand before sprinkling it on top of the cake to make small clumps. There is no need to be timid about ""clumping"" and spreading the streusel; it will taste fine no matter your method. (You may involve a child for this tactile experience.) Bake until the cake is golden on top, checking the cake with a toothpick after 50 minutes and every five minutes thereafter. Cool cake for at least 20 minutes before removing sides of pan and transferring to a cake plate. Serve warm or at room temperature."]
