Preheat oven to 350 degrees F (175 degrees C). Grease an 8-inch cake pan with cooking spray.
Combine almond milk and vinegar in a blender. Let stand until curdled, about 10 minutes. Add applesauce, dates, and vanilla extract; blend until smooth.
Mix whole wheat flour, 1/2 cup almond meal, baking powder, 2 teaspoons cinnamon, and salt together in a bowl. Pour in date mixture and stir until batter is combined.
Mix date syrup, walnuts, 1 cup almond meal, and 2 teaspoons cinnamon in a bowl to make topping.
Spread 1/2 of the batter in the prepared pan. Drop 1/2 of the topping evenly over the batter. Spread remaining batter on top. Swirl batter and topping together with a butter knife. Drop remaining topping on top.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 20 to 25 minutes.