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1
Preheat the oven to 350.
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2
Coat a 9-inch-square cake pan with vegetable oil spray.
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3
Make the crumbs In a food processor, pulse the brown sugar with the flour, cinnamon and salt.
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4
Add the butter and pulse until the mixture has a sandy texture.
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5
Add the oats and pecans and pulse until incorporated.
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6
Transfer the crumbs to a bowl and freeze until ready to use.
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7
Make the cake In a medium bowl, combine the flour with the baking powder, baking soda, cinnamon and nutmeg.
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8
Sift the mixture onto a sheet of parchment paper.
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9
In a large bowl, using an electric mixer, cream the butter with the brown sugar and salt at medium-high speed until fluffy, about 5 minutes; scrape the bowl.
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10
Add the sour cream and beat until smooth, about 2 minutes.
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11
Beat in the eggs one at a time at medium speed, scraping the bowl after each addition.
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12
Beat in the vanilla.
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13
At low speed, beat in the flour mixture in 3 additions, scraping the bowl as needed.
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14
Spread the batter in the prepared pan and scatter the frozen crumbs on top.
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15
Bake for 30 minutes, until golden brown and a toothpick inserted in the center comes out clean.
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16
Transfer to a wire rack and let cool.
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17
Cut into 12 squares and serve warm or at room temperature.
