I have to tell you, these truly are one of the best muffins I've tasted. They have a really robust blueberry flavor and the lemon sugar on the top is an added bonus! I will warn you though, it does have a lot of steps, and clean up took some time.....but all-in-all, I would say it was worth it.
For the lemon-sugar topping:
1/3 cup sugar
For the muffins:
2 cups fresh blueberries
1 1/8 cups plus 1 tsp. sugar
2½ cups flour
2½ tsp. baking powder
1 tsp. salt
2 large eggs
4 Tbsp. unsalted butter
¼ cup vegetable oil
1 cup buttermilk
1½ tsp. vanilla extract
(note: Per America's Test Kitchen - do not substitute frozen blueberries for fresh in this recipe)
1. Melt the butter. Set aside to cool
2. Adjust oven rack to upper-middle position and heat oven to 425 degrees. Spray standard muffin tin with nonstick cooking spray.
3. FOR TOPPING: Finely grate 1½ tsp. zest from 1 lemon. Transfer to small bowl. Stir in 1/3 cup sugar until combined. Set aside.
4. FOR MUFFINS: Bring 1 cup blueberries and 1 tsp. sugar to simmer in small saucepan over medium heat. Cook, mashing berries with wooden spoon several times and stirring frequently, until berries have broken down and mixture is reduced to ¼ cup, about 6 minutes. Cool to room temp.
5. Whisk 2½ cups flour, 2½ cup tsp. baking powder, and 1 tsp. salt together in large bowl.
6. Whisk remaining 1 1/8 cups sugar and 2 large eggs together in medium bowl until thick and homogeneous, about 45 seconds.
7. Slowly whisk in melted butter and ¼ cup vegetable oil until combined. Whisk in 1 cup buttermilk and 1½ tsp. vanilla extract until combined.
8. Using rubber spatula, fold egg mixture and remaining 1 cup blueberries into flour mixture until moistened. (batter will be lumpy with streaks of flour; don't overmix)
9. Divide batter equally among the prepared muffin cups. (batter should completely fill cups and mound slightly)
10. Spoon tsp. of cooked berry mixture into center of each mound of batter. Using chopstick or skewer, gently swirl filling into batter using a figure eight motion.
11. Sprinkle lemon sugar evenly over muffins.
12. Bake until muffin tops are golden and just firm, 17-19 minutes, rotating muffin tin from front to back halfway through baking time.
13. Cool muffins in tin for 5 minutes. Transfer to wire rack and cool 5 minutes before serving.
This was the first time I used truvia for baking, trying to minimize the sugar. I was pleased that I didn't taste any difference whatsoever. For us folks in high altitude, I did use the high altitude flour like I always do when I bake, and other than the tops not raising quite as high as (America's Test Kitchen) their picture, they held together well. The muffins had actually spread during baking and cooked together on top of the pan, so I was concerned about getting them out, but with a knife, I was able to do okay without any of them breaking apart. I need to do some research, since I would love to know what adjustment to make to get nice rounded tops in high altitude.