Topped with a cinnamon-laced streusel crunch, these tender sour cream muffins hide a swirl of rhubarb compote and lightly sweetened cream cheese in the center.
Preheat the oven to 400°F. Line the wells of a muffin pan with papers, and grease the insides of the papers. You'll have two extra muffins to bake, so use two 6-ounce ramekins as molds; or if you have one, a 6-well muffin pan. Or simply bake in two batches.
To make the filling: Whisk 1/4 cup of the sugar and the flour together in a small bowl. Place the rhubarb in a small saucepan with the lemon zest and pour the sugar/flour mixture over it. Bring to a simmer over medium heat and cook until the mixture boils and thickens, about 5 minutes. Remove from the heat and cool to room temperature. Mix the remaining tablespoon of sugar into the cream cheese until the mixture is smooth. When the rhubarb has cooled, swirl rhubarb and cream cheese together without completely mixing the rhubarb in.
To make the streusel: In a small mixing bowl, whisk together the sugar, flour, cinnamon, and salt. Stir in the butter and almond extract, mixing until the mixture forms crumbs. Set the mixture aside.
To make the batter: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set the mixture aside.
In a large mixing bowl, use an electric mixer to beat together the butter and sugar until they're light and fluffy and almost white in color. Scrape the bowl, then add the eggs one at a time, beating well after each addition.
Add the vanilla and sour cream and mix until incorporated. Add the dry ingredients and mix on low speed just until the batter is smooth.
To assemble: Portion the batter into the muffin cups, using 1/4 cup of batter for each. Use a wet finger or the back of a spoon to make a 1" deep indentation in the top of each one.
Scoop 1 tablespoon of cream cheese filling into each indentation (a teaspoon cookie scoop is very helpful here) and press it down slightly. Sprinkle the top of each muffin with 2 tablespoons of the streusel mixture, pressing it in just a bit to help it stick.
Bake the muffins for 22 to 25 minutes, until a cake tester or toothpick inserted into the center comes out clean. Remove from the oven and cool in the pan on a rack for 5 minutes, then tilt out of the pan and transfer to the rack to finish cooling completely.
Store any leftovers in the refrigerator, covered, for up to 1 week.
As is the case with any fresh fruit or vegetable, using fresh rhubarb rather than frozen will give these muffins optimum flavor.
