Note: If your kumquats are very seedy, you might want to start with more fruits than you think you'll need. Use the prettier, more intact slices for the tart and muddle the excess bits for Kumquat Spritzers. Also, I really like the bracing tartness of kumquats, but if you prefer something sweeter, there's a note at the end of the recipe with instructions for candying the citrus slices. You could also use thinly sliced Mandarin oranges instead of kumquats.
Kumquat Tarts with Almond-Date Crust
Makes 2 (4-inch) tarts
1 cup Greek yogurt
1/2 cup almonds, toasted
1/4 cup rolled oats
1/2 teaspoon ground cardamom
Pinch of salt
1 cup pitted dates
2 tablespoons honey
About 10 kumquats, sliced into rounds and seeded*
Special equipment: 2 (4-inch x 3/4-inch) tart pans with removable bottoms
Do ahead: Pour the yogurt into a fine-meshed strainer set over a bowl and allow to drain overnight in the refrigerator. (If you forget to strain the yogurt ahead of time, you can use straight Greek yogurt or strain it briefly. Your yogurt just won't be quite as thick.)
Preheat oven to 350°F.
Place almonds, oats, cardamom, and salt in the bowl of a food processor and pulse until mixture resembles coarse meal. Add dates and process until mixture comes together into a dough.
Divide dough into 2 equal pieces. Press 1 piece evenly onto bottom and up sides of each tart pan. (Use the bottom of a glass to smooth it down.) Bake until slightly browned and puffed up, about 12 minutes. Cool completely on rack.
When crusts are cool, remove from pans.
Combine yogurt and honey, and spread mixture evenly in the center of each crust.
Arrange kumquat slices on top. Serve immediately or refrigerate for up to a day.
*Note: If your kumquats are very tart, or if you just want a sweeter dessert, you can candy the slices. Combine 1/2 cup sugar and 1/2 cup water in a small saucepan, bring to a boil, then reduce to a simmer. Add kumquat slices and simmer for 10 minutes. Remove kumquats, shake off excess liquid, and toss them in sugar to coat.