Plum Kuchen

Ingredients

• 0.3 ounces active yeast dry
• 1 large eggs warmed
• 2 cups flour all-purpose divided
• 1.5 teaspoon lemon zest grated
• 0.8 pound firm-ripe plums pitted halved ( 4 small)
• 0.5 teaspoon salt 
• 0.5 cup whole-milk yogurt plain greek-style at room temperature (preferably )
• 8 servings accompaniment: whole-milk yogurt plain sweetened greek-style (preferably )
• 1 cup sugar divided
• 1.3 sticks butter unsalted divided softened cut into tablespoons and ,
• 1 teaspoon vanilla extract pure
• 0.3 cup warm water (105-110°F)

Equipment

• bowl
• frying pan
• oven
• blender
• plastic wrap
• baking pan
• kitchen towels

Directions

1. Stir together yeast and warm water in mixer bowl and let stand until foamy, about 5 minutes. (If mixture doesn't foam, start over with new yeast.)
2. Add 2 cups flour, 2/3 cup sugar, salt, yogurt, egg, zest, and vanilla to yeast mixture and mix at medium-low speed 1 minute. Beat in 1 stick butter, 1 Tbsp at a time, until incorporated. Beat at medium speed until dough is smooth and shiny, about 5 minutes. (Dough will be very sticky.) Scrape down side of bowl and sprinkle dough with remaining 2 tablespoons flour. Cover bowl with a kitchen towel (not terry cloth) and let dough rise in a draft-free place at warm room temperature until doubled, 1 1/2 to 2 hours.
3. Spread remaining 2 tablespoons butter in bottom of a 9-inch square baking pan and sprinkle with remaining 1/3 cup sugar.
4. Cut each plum half into 5 or 6 slices and arrange in 1 layer pan.
5. Stir dough until flour is incorporated, then spread evenly over plums. Loosely cover with buttered plastic wrap, then kitchen towel.
6. Let rise in a draft-free place at warm room temperature until almost doubled, about 1 1/2 hours.
7. Preheat oven to 375°F with rack in middle.
8. Bake until kuchen is golden-brown and a wooden pick inserted into center comes out clean, 30 to 35 minutes. Cool in pan 5 minutes, then invert and unmold onto a rack to cool completely.
9. Kuchen is best the day it is baked but can be kept, loosely covered, at room temperature 1 day.