Heat the oven to 350F.

Grease a 10 in tube pan with butter.

In a small bowl, whisk together the sugar, brown sugar and flour until well blended.

Stir in the almonds.

Add the melted butter and using a fork or your fingers, mix until evenly combined and the mixture starts to come together.

Set aside.

In a medium bowl, whisk together the flour, baking powder, baking soda, xanthan gum and salt until well combined.

Set aside.

In a large bowl, using an electric mixer on medium speed, cream the butter and sugar until light and fluffy, about 3 minutes.

Scrape down sides of the bowl.

Add the eggs, one at a time, beating well after each addition.

Scrape down sides of the bowl.

Stir in the almond extract.

Add the flour mixture and the sour cream to the butter-sugar mixture, stirring between each addition until blended.

Mix until smooth, about 30 seconds.

Spoon half the batter into the prepared pan.

Sprinkle ⅔ of the streusel mixture over the batter.

Top with the remaining batter and spread smooth.

Crumble the remaining streusel over the top of the batter.

Bake until golden brown and a wooden pick inserted into the center comes out clean, 55 minutes.

Let the cake cool in a pan on a wire rack for 5 minutes.

Gently run a knife blade between the cake and the edge of the pan to loosen.

Remove the sides and center of the pan and transfer the coffee cake onto a wire rack to cool.

In a medium bowl, combine the powdered sugar, half-and-half, butter and almond extract.

Beat with a whisk until smooth and spreadable.

Spread or drizzle the icing over the cake.