For The Cake: Preheat oven to 350°. Spray a 15-cup Bundt pan with nonstick baking spray with flour; set aside.
In a large bowl, beat butter at medium speed with an electric mixer until creamy, about 3 minutes. Add sugars and vanilla, beating until fluffy, about 3 minutes. Add eggs, one at a time, beating well after each addition.
In a medium bowl, whisk together flour, baking powder and salt. Gradually add flour mixture to butter mixture alternately with milk, beginning and ending with flour mixture. Spoon batter into prepared pan.
Bake for 45 minutes; loosely cover with aluminum foil and continue baking until a wooden pick inserted near the center comes out clean, about 45 minutes.
Remove from oven and cool in pan on a wire rack 10 minutes. Remove from pan and cool completely on wire rack. Drizzle cake with Salted Caramel Sauce and sprinkle with about 1 cup Pecan Toffee pieces. Store at room temperature up to 5 days.
For The Salted Caramel Sauce: In a medium saucepan, combine condensed milk and brown sugar. Bring to a boil over medium-high heat, whisking often. Reduce heat to medium-low and simmer 5 to 8 minutes, whisking often. Remove from heat; whisk in butter, vanilla and sea salt. Cool at least 20 minutes before using. Makes about 1 1/2 cups.
For The Pecan Toffee: Butter a large rimmed baking sheet; set aside.
In a large saucepan, combine sugar, butter, 1 cup water, vanilla and salt. Bring to a boil over medium-high heat; boil until a candy thermometer reads 285° or soft-crack.
Pour onto prepared baking sheet. Sprinkle with pecans and let stand until set, about 30 minutes.
Break into small pieces. Makes about 4 cups. Store in an airtight container at room temperature up to 5 days.