Morning eggs are cooked in lard. Lard from pastured pigs is a good source of D, as are yolks from pastured chickens. If lard isn't your thing choose some good grass-fed butter (we use Kerrygold and Organic Valley). Cod liver oil is another source we use, and I also choose to take a Vitamin D supplement.
Many people are deficient in Vitamin D. I’m not a doctor, but this is what we do in our house.