Preheat oven to 350 degrees and line a 9 x 9 inch cake pan with parchment with about two inches overhanging the edges.
In the bowl of a stand mixer or with a hand mixer, cream butter and brown sugar for 2 minutes until fluffy. Beat in honey, Greek yogurt, vanilla, lemon zest, and lemon juice. Whip eggs into the mixture one at a time.
In a separate bowl, sift together flour, baking powder, baking soda, and salt.
In three turns, alternate flour mixture and milk, beating until mostly mixed in between. So, you'd do one round of flour mix, one round of milk, one round of flour, one round of milk, then the final round of flour and the final round of milk.
In a third small bowl, whisk together the streusel ingredients. Mix briefly with hands to create larger crumbs.
Pour half of the cake batter into prepared baking pan. Dollop blueberry jam across the top and spread with a spatula until evenly distributed. Clean and grease the same spatula or a new one and spread the remaining cake batter over the jam. Sprinkle streusel until the cake is fully covered.
Bake 45-55 minutes or until toothpick inserted into the center comes out clean.
Remove from oven and cool in the pan for 5 minutes, then grab the parchment and transfer to a wire baking rack to cool completely. Slice into 12 pieces and serve with a hot mug of coffee!