1. Center a rack in the oven and heat to 375 degrees. Wrap beets tightly in heavy duty foil and place on a baking sheet. Roast until a paring knife easily pierces through to centers, 45 to 75 minutes. Let cool completely.
2. Reduce oven temperature to 325 degrees. Melt butter in a medium skillet over medium heat and cook, swirling occasionally, until sputtering subsides. Continue to cook, scraping bottom of skillet frequently, until butter turns golden brown and smells nutty, 5 to 7 minutes. Working quickly, scrape butter and browned solids into a heatproof measuring cup; set aside.
3. To make streusel, combine 3/4 cup flour, 1/2 cup brown sugar, cinnamon, and salt in a medium bowl; stir in hazelnuts. Stir brown butter to evenly distribute solids then add 6 tablespoons to streusel mixture and stir until large clumps the size of marbles form. Cover and refrigerate until mixture is firm but still crumbly, about 15 minutes.
4. Peel and coarsely chop beets and transfer to a food processor. Add milk and lemon juice and pulse until finely chopped, about 10 times. Add remaining 16 tablespoons brown butter and eggs and puree until completely smooth, scraping down bowl as needed, about 60 seconds.
5. Whisk remaining 1 3/4 cup flour, granulated sugar, remaining 1/2 cup brown sugar, baking powder, baking soda, and remaining 1/2 teaspoon salt in a large bowl. Add pureed beet mixture and stir until just combined. Pour batter into a greased 8x8" baking pan and smooth surface with a greased spatula. Sprinkle streusel evenly over batter and bake until a toothpick inserted in center of cake comes out clean, about 1 hour.
6. Transfer pan to a wire rack and let cool completely, about 2 hours. To serve, dust cake evenly with confectioners' sugar and cut into squares.
Source: Hannaford fresh Magazine, May - June 2018