Preheat oven to 325°F. Butter and flour a 14-cup Bundt pan.
Make Froot Loops Streusel: Place Froot Loops in a large zip-top bag; use a rolling pin to crush into pea-sized pieces.Whisk together all-purpose flour (spooned and leveled), sugar, lemon zest, and kosher salt in a bowl. Cut cold unsalted butter into flour mixture with a pastry blender or two forks until mixture resembles small peas. Stir in crushed cereal, omitting fine powder in bottom of bag.
Whisk together flour, salt, and baking powder in a bowl. Beat butter and sugar on medium speed with an electric mixer until light and fluffy, 1 to 2 minutes. Add cream cheese and beat until creamy, 1 to 2 minutes. Add eggs, 1 at a time, beating just until blended after each addition. Beat in lemon zest and juice, orange zest, and vanilla. Reduce mixer speed to low and gradually add flour mixture, beating just until blended. Pour half the batter into prepared pan. Top with Froot Loops Streusel, leaving a thin border around the edge; top with remaining batter.
Bake until a wooden pick inserted in center comes out clean, 60 to 70 minutes. Cool in pan on a wire rack, 15 minutes. Transfer to wire rack and cool completely.
Make Citrus Glaze: Combine confectioners’ sugar, pure vanilla extract, and kosher salt in a bowl. Whisk in fresh lemon juice, a little at a time, until desired consistency is reached.
Spoon Citrus Glaze over cake and sprinkle with Froot Loops.