Easy Apple Cake

Ingredients

• 2 large eggs
• 1 cup (200 g) granulated sugar
• 1 tsp. baking powder
• 1 tsp. vanilla bean paste or vanilla extract
• 2 tsp. ground cinnamon, divided
• ½ cup sour cream
• 2 Tbsp. apple cider vinegar
• Nonstick vegetable oil spray or unsalted butter, room temperature (for pan)
• Special Equipment: a 9"-diameter springform pan
• ½ cup (1 stick) unsalted butter, room temperature
• ½ cup raw walnuts
• 1½ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt, divided
• 2¼ cups (281 g) all-purpose flour
• 3 large Honeycrisp or Fuji apples (about 1½ lb.), peeled, cored, cut into ½" pieces
• ½ cup (100 g) dark brown sugar