Preheat the oven to 350°F (175°C). Grease an 9x9-inch baking pan or line with parchment paper.
Place dates in a bowl and cover with hot water. Let soak for 5 minutes, then drain and mash into a paste.
In a large bowl, cream together (mix) the butter and brown sugar until light and fluffy.
Add the eggs and beat until smooth.
Stir in the flour, baking powder, and cinnamon until just combined.
Fold in the mashed dates until evenly incorporated.
Pour the batter into the prepared pan and bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean.
While the cake bakes, make the butterscotch sauce: In a saucepan over medium heat, combine the brown sugar, butter, and heavy cream. Stir until everything is melted and smooth (about 3–4 minutes).
Remove the cake from the oven and use a straw or fork to poke holes all over the surface.
Pour the warm butterscotch sauce evenly over the cake, letting it soak in.
Let rest for 5–10 minutes before serving.
Serve hot with vanilla ice cream and a sprinkle of flaky sea salt!
To reheat simply microwave a slice for 30 seconds.