Preheat your oven to 350 °F (175 °C) and grease the loaf pan. In a bowl, beat softened cream cheese with sugar, eggs, lemon juice, and vanilla until creamy and smooth.
In another bowl, stir together the lemon cake mix and lemon instant pudding (don’t add milk, as per box). Add the dry mix into the cream cheese mixture and fold gently until combined — don’t overmix.
Pour the batter into your prepared loaf pan and smooth the top. Bake for 50–60 minutes or until a toothpick comes out clean. Let it rest in the pan ~10 minutes, then transfer to a rack to cool completely before glazing or slicing.