And oh, did I find a recipe - a really, really good recipe, which I am about to share with you - here on food.com.
This is half of the batter, with the "tunnel" of streusel around the center, before the other half of the batter was poured on top.
This was a fantastic cake, we ate a fourth of it before lunch, before I could make the glaze! Ended up not making the glaze since it was so good without it. This cake is not too heavy, not too pumpkin-y, just the right balance of spices and sweetness.
I substituted 1/2c applesauce for 1/2c of the butter, and I used plain yogurt instead of the sour cream, to significantly reduce the fat. I was very pleased with the results... so delicious!
Now I'm trying to decide if I want to make this cake again, or finally make an autumn apple pie!