• For Crumble Topping:
• 2 Tablespoons unsalted butter, melted
• 1/ 4 cup flour
• 2 Tablespoons brown sugar
• 1/ 4 cup chopped pecans
• 1/ 4 teaspoon sea salt
• For Cake:
• 1 stick unsalted butter, +more for pan
• 2 peaches, sliced
• 1/ 2 cup powdered sugar
• 1/ 2 cup light brown sugar
• 1 cup flour
• 1 teaspoon baking powder
• 1/ 2 teaspoon salt
• 1/ 2 teaspoon grapefruit zest, finely
• 1 Tablespoon grapefuit juice
• 1/ 2 teaspoon vanilla
• 1 egg
• 1 egg white
• 1/ 2 cup plain yogurt + 2 Tablespoons

Preheat oven to 350°F with a shelf placed in the upper third of the oven. In a small bowl, prepare the crumble topping: combine melted butter, flour, sugar, pecans and ¼ tsp salt until moist and crumbly. Set aside.

Butter the Fruit Tartine Pan. Cut 4 Tbsp of butter into small pieces and scatter them across the bottom of the greased pan. Do not use parchment paper. Clean and slice peaches into long slices to fit into fruit design of the pan; toss with ½ cup powdered sugar and let stand for 2 minutes. Toss again, and place peach slices into fruit wedge design on top of butter dots, in a fan-like formation around the bottom of the pan. If there is juice at the bottom of the bowl, be sure to pour that in, too. Cream remaining stick butter and 1/2 cup of brown sugar with a mixer on medium speed until flu y, about 3 minutes. Beat in zest, juice, and vanilla. Beat in eggs, 1 at a time, until incorporated, scraping down sides of bowl. Add baking powder and salt, mixing thoroughly. Beat in flour in 3 additions, alternating with plain yogurt, until smooth. Do not overmix! Spread mixture evenly over peaches in the prepared pan. Scatter the crumble topping evenly over batter.

Bake 35-40 minutes or until toothpick inserted into the center comes out clean and top springs back when touched. Let cool for just 10 minutes or sugars will solidify and cake will not release from pan. Run a knife around edge of the pan, and invert onto a wire rack or serving plate. May be served warm or cold, depending on preference, with remaining peach slices or whipped cream.