Preheat the oven to 350 degrees F and grease a large bundt pan with cookie spray, place the pan on a rimmed baking sheet and set aside.
Add the semi-sweet chocolate to a microwave safe bowl and microwave on 30-second intervals, stirring between each until melted. Usually, about 90 seconds works for me, once the chocolate has melted about 90% of the way, just continue to stir and the rest with melt without further microwaving.
In a large bowl or stand mixer fitted with a whisk attachment, mix together the melted chocolate, sugar, and applesauce. Whisk in the eggs one at a time and then whisk in the yogurt and vanilla extract until fully incorporated.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Add the flour mixture to the yogurt mixture and mix just until combined. The batter will be thick.
Spread the batter out in the prepared bundt pan and bake for 45 to 55 minutes or until a toothpick inserted into the center of the cake comes out clean. Remove from the oven and allow to cool in the pan for 10 minutes.
Flip the cake onto a cooling rack to release the cake from the pan and then allow the cake to cool for 2 hours before making and topping with the ganache.