Apple Crumble Cake from The Official Downton Abbey Afternoon Tea Cookbook by Downton Abbey

Ingredients

• 1 teaspoon baking soda
• 3 cups (375 g) flour, plus more for the pan
• ¼ teaspoon salt
• 1 teaspoon ground cinnamon
• 1 cup (210 g) firmly packed light brown sugar
• 1 cup (200 g) granulated sugar
• ¾ cup (170 g) unsweetened applesauce
• ¾ cup (180 ml) canola oil
• 3 baking apples, peeled, cored, and cut into cubes
• 3 eggs
• ½ cup (115 g) cold unsalted butter, cut into cubes
• 1 cup (125 g) flour
• ½ cup (100 g) firmly packed light brown sugar
• Unsalted butter, for the pan