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1
For salted caramel sauce:
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2
Bring sugar and 1/4 cup water to a boil in a small saucepan over medium-high heat, stirring to dissolve sugar.
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3
Boil, swirling pan occasionally and brushing down sides with a wet pastry brush, until mixture turns a deep amber color, 8-10 minutes.
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4
Remove from heat and slowly add cream (mixture will bubble vigorously). Return to medium heat and cook, stirring occasionally, until smooth, about 2 minutes.
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5
Remove from heat and mix in butter and salt.
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6
Pour caramel sauce into a small heatproof jar or bowl; let cool.
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7
For cake:
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8
Place rack in middle of oven and preheat to 350u00b0F Butter and flour cake pan; set aside.
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9
Heat 2 tablespoons melted butter in a large skillet over medium heat.
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10
Add apples, sprinkle with 2 tablespoons sugar, and cook, tossing occasionally, until apples are golden brown, 10-12 minutes.
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11
Arrange half of the apples in the bottom of prepared cake pan so most of it is covered (a few gaps are okay).
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12
Whisk baking powder, salt, lemon zest, 1 1/4 cups flour, and remaining 1 cup sugar in a large bowl.
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13
Whisk in eggs and remaining 10 tablespoons melted butter until smooth.
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14
Pour half of batter over apples in an 8-inch diameter cake pan, top with remaining apples, then pour remaining batter over.
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15
Bake cake until top is golden and a tester inserted into the center comes out clean, 40-50 minutes.
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16
Transfer pan to a wire rack and let cake cool slightly; turn out onto rack and let cool.
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17
Serve cake with caramel sauce and creme fraiche.
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18
DO AHEAD: Caramel sauce can be made 5 days ahead. Cover and chill. Cake can be baked 1 day ahead. Keep wrapped tightly at room temperature.
