Preheat your oven to 350°F. Line a 9 inch (round or square) cake pan with parchment paper, and set aside.*For a thicker cake, you can use an 8 inch pan, but it will take slightly longer to bake.
In a medium bowl, combine flour, baking powder, baking soda, and salt. Whisk to combine, and set aside.
In a large bowl, combine butter, sugar, and vanilla. Beat together until you no longer see any streaks of butter or dry granules of sugar. The mixture won't be light and fluffy - it should be quite crumbly.
Add your eggs to the butter mixture one at a time, whisking well after each addition.
Alternate adding dry ingredients and milk/yogurt to the butter mixture. Start by adding about 1/2 of the dry ingredients, and mixing them in. Then add your milk and yogurt, and mix until combined. Finish off by adding the remaining 1/2 of the dry ingredients, and mix until just combined.
Pour the cake batter into your prepared cake pan. Bake in the center of your preheated 350°F oven for 20 to 25 minutes, or until golden brown on top and a skewer inserted into the center of the cake comes out clean.
Cool the cake for about 10 minutes in the pan, and then transfer onto a wire rack to cool completely to room temperature. Once cool, spread a layer of your favorite jam on top of the cake, then sprinkle your coconut on top.