• Preheat oven to 350°F. Grease 9x13-inch (23x33 cm) baking pan and line with parchment paper with a little overhang on two longest sides.
• In bowl, add apples. In small bowl, combine granulated sugar, cinnamon, nutmeg and salt; set aside.

Cake

• In another bowl, whisk together flour, baking powder and salt.
• In large bowl, whisk together oil, eggs, granulated sugar and brown sugar until light and incorporated, 30 to 45 seconds. Whisk in flour mixture in two increments until smooth.
• Toss apples with sugar-cinnamon mixture; immediately fold into cake batter until just combined. Scrape into prepared pan; spreading evenly. Bake until cake tester inserted into centre comes out clean, 45 to 55 minutes.
• Let cook on rack for 30 minutes. Using a paring knife, loosen edges; carefully lift parchment onto rack to cool.

Toffee Glaze

• In saucepan, cook butter, brown sugar, cream and salt over medium heat, stirring, until melted. Add nutmeg; bring to a boil and cook for 1 minute. Reduce heat and simmer for 30 seconds; remove from heat, add icing sugar and whisk until smooth. Let cool enough to thicken, 15 to 20 minutes.
• Pour over cake, spreading evenly. Immediately sprinkle with pecans (if using) and sprinkle over flaked sea salt (if using) once topping sets a little.