Portion the beef mixture among the 8 tortillas. Roll each tortilla tightly around its filling, then place the rolled enchiladas seam side down in the prepared baking dish.
In a bowl, combine the sour cream and enchilada sauce. Whisk until smooth and well combined. Pour the sauce over the enchiladas in the baking dish.
Sprinkle the shredded Mexican blend cheese over the enchiladas.
Cover with foil and bake for 15 minutes.
Remove the foil and continue baking for another 5-10 minutes, until the sauce is bubbling around the edges, the cheese is melted, and the tops of the enchiladas look slightly golden and set.
Remove from oven and let the dish rest for 5-10 minutes before serving.