For the toffee cake:
8 ounces pitted dates, coarsely chopped (about 1 1/4 cups chopped)
1 cup water
1 teaspoon baking soda
4 ounces (8 tablespoons) unsalted butter, room temperature
1 cup packed dark brown sugar
2 large eggs, room temperature
10 ounces all-purpose flour (approximately 2 cups)
1/2 teaspoon baking powder
1/4 teaspoon fine sea salt
1/2 teaspoon vanilla bean paste or pure vanilla extract
1/2 teaspoon coffee extract, such as Trablit (optional)
For the caramel sauce:
4 ounces (8 tablespoons) unsalted butter, room temperature
1 cup packed dark brown sugar
1 cup heavy cream
1 tablespoon spiced rum or bourbon (optional)
2 teaspoons vanilla bean paste or pure vanilla extract
For the sundaes:
Vanilla ice cream
Toasted, chopped pecans
Whipped cream
Toffee bits, such as Heath or Skor
Combine the chopped dates and water in a small saucepan and bring to a boil. Remove from the heat. Stir in baking soda and let stand for a minimum of 20 minutes, or up to two hours. Transfer half of the mixture to the bowl of a food processor or blender and process until pureed. Return puree back to the date mixture and set aside.
Preheat oven to 375° F. Generously grease the bottom and sides of an 8-inch square baking dish with butter or baking spray.
In the bowl of a stand mixer fitted with paddle attachment (or with an electric mixer), cream together the butter and sugar on medium speed until light and fluffy, 3 to 5 minutes. Reduce speed to low and add the eggs one at a time, fully incorporating after each addition. Stop the mixer and scrape down the sides of the bowl.
Whisk the dry ingredients together in a separate mixing bowl. On low speed, alternate adding the dry ingredients with the date mixture, beginning and ending with the dry ingredients. Stir in the vanilla and coffee extract. Pour the batter into the prepared pan and smooth with a spatula.
Place the baking dish inside a larger casserole dish or roasting pan and transfer to the oven. Pour enough hot water to reach halfway up the side of the cake dish. Bake until a toothpick pricked into the middle comes out slightly moist, 35 to 40 minutes.
When the cake has about 10 minutes left of cooking time, make the caramel sauce. Combine butter, sugar, and cream and a heavy saucepan. Whisking constantly, bring the mixture to a boil and cook for 3 minutes. Remove from the heat and whisk in rum (if using) and vanilla.
Remove the cake from the oven and allow to cool for 5 minutes. Prick the cake all over with a skewer or toothpick. Pour half the sauce over the warm cake and let