Get out and measure all of your ingredients. Allow eggs, butter and cream cheese to come to room temperature so take them out first, about 30 minutes before needed.
Preheat your oven to 325 degrees. Heavily spray 12-cup nonstick Bundt pan with baking spray and flour.
Make lemon zest and set aside.
Whisk flour, baking powder, baking soda, salt, and cinnamon together in large bowl. Whisk buttermilk, lemon zest and juice, and vanilla together in medium bowl.
Gently whisk eggs and yolk to combine in third bowl.
Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes, scraping down bowl as needed.
Reduce speed to medium and beat in half of eggs until incorporated, about 15 seconds. Repeat with remaining eggs, scraping down bowl after incorporating.
Reduce speed to low and add one-third of flour mixture, followed by half of buttermilk mixture, mixing until just incorporated after each addition, about 5 seconds. Repeat using half of remaining flour mixture and all of remaining buttermilk mixture. Scrape down bowl, add remaining flour mixture, and mix at medium-low speed until batter is thoroughly combined, about 15 seconds.
Remove bowl from mixer and fold batter once or twice with rubber spatula to incorporate any remaining flour. Cover bowl with plastic wrap and set aside while preparing filling (batter will inflate a bit).