Combine flour, oatmeal, baking soda, and salt in a deep bowl. Add both types of sugar, stir. Pour in melted butter, vanilla, and stir thoroughly until all ingredients are wet.
Place parchment on an 8 * 8-inch baking dish and place half of the oatmeal dough there. Press evenly filling all edges and place in an oven preheated to 350F for 15 minutes. Cool it down.
In a bowl, combine the condensed milk, vanilla, lemon juice and zest, yolks. Mix until smooth. Pour over the baked crust, crush the remaining half of the dough on top, covering the entire filling. Bake for another 25 minutes. Cool on a wire rack and refrigerate for at least an hour. Remove from the mold, cut into portions, and serve.