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1
Position a rack in the middle of the oven and preheat to 400 degrees F. Line 12 standard muffin cups with paper liners, or grease with cooking spray.
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2
To make the streusel, in a bowl, stir together the melted butter and vanilla.
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3
In another bowl, combine the flour, sugar, and salt and stir together with a fork.
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4
Add the butter mixture and stir until evenly blended and crumbly.
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5
Use right away or refrigerate, covered, until ready to use.
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6
In a bowl, sift together the flour, baking powder, baking soda, and salt.
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7
In the bowl of a mixer fitted with the paddle attachment, beat the butter, sugar, and lemon zest on medium-high speed until fluffy, about 1 minute.
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8
Beat in the eggs, one at a time, then the vanilla, until well combined, scraping down the sides of the bowl with a rubber spatula.
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9
Add the sour cream and beat on low speed.
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10
Add the dry ingredients and, using the rubber spatula, stir just until evenly moistened.
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11
Gently fold in the berries.
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12
The batter will be very thick.
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13
Using an ice cream scoop, heap the batter into the prepared muffin cups, filling them full.
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14
Sprinkle the streusel over the tops of the muffins, dividing it evenly and pressing it down to stick to the batter.
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15
Bake until the muffins are golden brown and a toothpick inserted into the center of one comes out clean, about 15 minutes.
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16
Let the muffins cool in the pan on a wire rack for 5 minutes, then turn out onto the rack.
