Preheat the oven to 400F. For the dry ingredients, sift flour, baking powder, and salt together in a small bowl. Set aside.

Using a stand mixer with paddle attachment or a hand mixer on low speed, cream together butter and granulated sugar together until smooth and incorporated. Add eggs one at a time, scraping the sides between each addition, and mix until fully incorporated. Add crème fraîche and mix until combined.

Starting at low speed, add dry ingredients in 2 stages, scraping sides between each addition. Using a spatula, gently fold in 100g (¾ cup) blueberries. Pour batter into prepared dish, and sprinkle the remaining 65g (heaping ½ cup) blueberries over the top.

Bake until the top of the cake is golden brown and a cake tester comes out clean, 35–40 minutes.  If using a thermometer, the center of the cake should read 200F.

While the cake is baking, prepare the blueberry compote. Combine blueberries, granulated sugar, and lemon juice in a 2 QT Saucier or Saucepan over low heat. Simmer until the blueberries start to break down, about 10 minutes. Chill in the refrigerator for at least 30 minutes.

For the glaze, sift powdered sugar into medium-sized bowl, then whisk in lime juice, and rumchata, if using. Set aside.

Remove cake from oven and leave in its dish to cool completely, then place in the refrigerator to chill for 1 hour. Ice cake with an offset spatula and return to the fridge for at least 1 hour or preferably overnight until the glaze is completely hard. Slice with a Paring Knife and drizzle sections with blueberry compote.