For topping: In a medium bowl, whisk collectively flour, granulated sugar, cinnamon, and salt. Utilizing a fork, stir in melted butter and vanilla till nicely mixed and combination is crumbly. Refrigerate till prepared to make use of.
Preheat oven to 350°F (180°C). Spray an 8-inch sq. baking pan with baking spray with flour. Line pan with parchment paper, letting extra prolong over all sides of pan.
For cake: Within the bowl of a stand mixer fitted with the paddle attachment, beat butter, granulated sugar, ¼ cup (55 grams) brown sugar, and oil at medium pace till gentle and fluffy, 3 to 4 minutes, stopping to scrape backside and sides of bowl. Add eggs, separately, beating nicely after every addition. Beat in vanilla.
In a medium bowl, whisk collectively flour, baking powder, salt, and baking soda. With mixer on low pace, steadily add flour combination to butter combination alternately with bitter cream, starting and ending with flour combination, beating till simply mixed after every addition and stopping to scrape backside and sides of bowl.
In a small bowl, whisk collectively cinnamon and remaining ¼ cup (55 grams) brown sugar.
Unfold half of batter (about 2½ cups or 595 grams) into ready pan. Sprinkle cinnamon sugar onto batter, leaving a ½-inch border on all sides. Utilizing an offset spatula, rigorously unfold remaining batter onto cinnamon sugar. Sprinkle topping throughout batter.
Bake till edges are golden brown and an instant-read thermometer inserted in middle registers 205°F (96°C), 1 hour to 1 hour and 10 minutes. Let cool in pan for 10 minutes. Utilizing extra parchment as handles, take away from pan, and let cool barely on a wire rack. Finest served heat. Garnish with confectioners’ sugar, if desired. Retailer in an hermetic container for as much as 3 days.
