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1
Preheat the oven to 350 degrees (325 degrees for a dark-finish pan).
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2
Line a 10-inch springform pan with parchment, grease the bottom and sides and set aside.
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3
To make the crumb top, in the bowl of a heavy-duty electric mixer fitted with the paddle attachment, combine the flour, sugar; and cinnamon.
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4
Cut in the vanilla and cold butter on low speed until coarse dry crumbs are formed.
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5
Pour into a small bowl and set aside.
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6
If not using immediately, refrigerate until needed.
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7
To make the cake batter, without cleaning the mixing bowl, cream the butter and sugar on medium speed until light and fluffy, about 1 minute.
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8
Add the eggs, one at a time, and the vanilla extract and beat well on medium speed for 30 seconds.
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9
The mixture will be loose.
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10
Add the flour; cinnamon, baking powder; baking soda, and salt and beat on low speed for 15 seconds.
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11
Add the sour cream and beat on medium-high speed only until the lumps smooth out and the mixture looks fluffy, about 30 seconds on medium-high speed.
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12
Do not overbeat.
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13
Spread the batter evenly into the prepared springform pan.
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14
Sprinkle the top evenly with the crumb topping.
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15
Bake on the center rack of the oven for 45 to 55 minutes, or until the top is crisp and feels firm when gently touched in the center; the cake separates slightly from the sides of the pan, and a cake tester inserted into the center comes out clean (it may be a bit moist; that's okay).
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16
Do not overbake, or the cake will be dry.
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17
Remove from the oven and cool in the pan on a wire rack for 5 minutes before removing the sides of the pan.
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18
Let cool at least 30 minutes before serving warm, or cover in plastic wrap to serve later at room temperature.
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19
Store at room temperature for up to 3 days.
