Cinnamon Coffeecake Muffins

It's Alex and my day off today, which is nice. I got up early to walk puff and had been dreaming of cinnamon-swirl coffeecake, so I decided to make it while Alex was still asleep. I keep forgetting to buy the ingredients for my flour mix, and am all out of potato starch and tapioca starch, but luckily I have a few boxes of Fearn Brown Rice Baking Mix, which I haven't used much, but I think it's great. I've accumulated a bit of it because I keep buying it when it's on sale, because it's pretty cheap, compared to other gf mixes. And it doesn't have bean flours in it, which I can't stand.
In important life news, Alex and I have found a house to move into when our lease is up in a month, after a lot of stress and headache on my part. It's tough finding a place now, because we have so much furnature we need something bigger than a 1 bedroom, and we have a bunch of pets. I'm spoiled by having a yard, so what we were really looking for was a house, or a two bedroom on the ground floor. Finally we found it, and it's in our neighborhood, four blocks south of where we live now. So we're still near the two take-out places we love, as well as being SUPER close to Target and Shop-Rite, our grocery store which, surprisingly, has a lot of gluten-free and natural foods. Plus we're still near the park where I walk Puff, which hopefully is getting a dogpark soon. We're pretty excited. And I think a friend of mine from work is going to come take care of the animals while we're in Europe, so now I can be excited about my one month trip to central Europe!! I'm starting to read guidebooks and websites. If you have any suggestions, on anything, again, let me know!!

Cinnamon Coffeecake Muffins
1 stick butter, softened
1 c brown sugar
2 eggs, slightly beaten
2 c Fearn Brown Rice Flour Mix (or, alternately, 2 c rice flour mix, 1 t baking powder, 1 t baking soda, 1 t xanthan gum)
1 t vanilla
1 c sour cream
Topping:
1/2 c brown sugar
2 t cinnamon
1/4 c nuts (of your choice, optional)

Beat butter and sugar, then add eggs. Mix in flour, then vanilla and sour cream, and beat until completely mixed. Scoop with an ice cream scoop or plop with spoons into a greased muffin tin, if you have extra, grease some ramekins and use those for the rest of the batter. Mix the topping ingredients, and sprinkle on top, then bake at 375 for 15-20 minutes, until they start to brown and a toothpick or thin knife inserted in comes out clean.