Remove the pits and chop the dates in small pieces. (This part will be sticky and messy but just do the best you can. It doesn't have to be perfect!) Add the chopped dates and water to a small saucepan.
7 oz (195 g) finely chopped Medjool dates (about 10 large dates), 1 cup (240 ml) filtered water
Bring the dates to a simmer over medium low and then let the mixture simmer for 10-12 minutes until thick and resembling jam (see photos). Mash the dates with a rubber spatula or wooden spoon while they simmer. The mixture should be about 1 1/4 cups worth or roughly 320 g once done cooking. Remove the date mixture from the heat and let it cool to room temperature.
Preheat the oven to 350 degrees F (180 degrees C). Spray a 9x9 inch (23x23 cm) pan with non-stick spray and line it with parchment paper.
In a medium bowl, combine the flour, baking powder, baking soda, and salt. Then set aside the flour mixture.
2 1/4 cups (281 g) all-purpose flour, spooned and leveled, 1 1/2 tsp baking powder, 1/4 tsp baking soda, 1/2 tsp salt
Add the granulated white sugar, brown sugar and butter to a large bowl. Cream together for 2 minutes with an electric mixer on high speed. (You can also use the bowl of a stand mixer fit with a paddle attachment.)
10 tbsp (140 g) unsalted butter, softened, 1/2 cup (100 g) granulated white sugar, 1/2 cup (110 g) light brown sugar, packed
To the butter mixture, add in the eggs, molasses and vanilla and mix on medium speed until pale in color and smooth, about 1 minute.
3 eggs, at room temperature, 1/4 cup (85 g) unsulphured molasses, 1 tsp vanilla
Add in the date mixture and mix on medium speed until combined. The batter will look separated at this point but it will pull back together once the dry ingredients are added in.
Add the dry ingredients and buttermilk a little bit at a time to the molasses mixture, mixing on low speed just until all is combined and the batter is smooth. Scrape the sides of the bowl with a rubber spatula as necessary.
3/4 cup (180 g) buttermilk, at room temperature
Pour the cake batter into the prepared pan. Bake the cake for 42-45 minutes or until a cake tester comes out clean from the center. (44 minutes is usually perfect.)
Let the warm cake cool in the pan on a wire rack until completely cool.