Nerd and Healthnut: Apple Yogurt Cake

Aaron and I have barely seen each other this whole week. He is studying so hard for the first actuary exam, as well as applying for internships and preparing for interviews. He is also a youth leader in our church which takes up his Wednesday nights and some Saturdays (which is the only day we have time to spend together...).
I haven't been too busy, just trying to find things to do while he studies. Baking, photography, reading, and some more baking. Here's one of my favorite recipes I tried this weekend. It was delightful to say the least.

Apple Yogurt Cake
Adapted from this recipe

1/3 cups (150 grams) whole wheat flour
1/4 tsp cinnamon
1/4 tsp salt
1/4 cup + 1 Tbsp (115 grams) brown sugar
4 tbsp unsalted butter, melted
4 Tbsp coconut oil
7 Tbsp applesauce
2 large eggs
1/2 cup yogurt
2 apples, peeled, cored, and thinly sliced
zest of 1 lemon

Topping
2 Tbsp chopped walnuts
1/4 tsp cinnamon
2 tsp brown sugar

Preheat the oven to 350°F. Butter an 8-inch cake round.
In a medium bowl, whisk together the flour, cinnamon, and salt.
In the bowl of an electric mixer fitted with the paddle attachment, beat sugar, butter, and coconut oil until it has lightened. Slowly add applesauce and beat until creamy.
Add the eggs, one at a time, beating between each addition and scraping down the bowl as needed.
Reduce the mixer speed to low and add the flour mixture alternately with the yogurt, beginning and ending with the flour.
Stir in the sliced apples and the lemon zest, and pour the batter in the prepared pan.
Mix the topping together and spread evenly over the top of the cake.
The original recipe suggests a baking time of 40 minutes, but I think it needs to bake for over one hour (until a tester inserted into the center (not through an apple if possible!) comes out clean.
Let cool completely before serving.