How to Make It
Preheat the oven to 350°. Butter a 9-inch square baking pan. In a large bowl, whisk the flour with the sugar, baking powder, baking soda and salt. In a small bowl, combine the oil, whole egg, milk, lemon juice and zest. Using an electric mixer, beat the wet ingredients into the dry ingredients just until they're evenly moistened. Scrape the batter into the pan.
In a medium bowl, beat the cream cheese with the egg yolk, sugar, lemon juice and zest. Spoon the cheesecake mixture onto the batter in clumps and gently swirl three times with a table knife.
In a small bowl, combine the flour and sugar with the butter and a pinch of salt. Press into clumps and sprinkle over the batter. Bake for 45 to 50 minutes, until the loaf is golden and risen and a toothpick inserted in the center comes out with a few moist crumbs attached. Transfer the pan to a rack and let cool for 30 minutes, then cut the cake into squares and serve.