Prep the pan and oven. Preheat your oven to 350°F (175°C). Grease and line an 8x8-inch square pan or a 9-inch round pan with parchment. Lightly greasing the parchment helps the cake release cleanly.

Whisk the eggs. In a large bowl, whisk the eggs for 20–30 seconds until slightly frothy. This helps the cake rise and feel light.

Add the lemon pie filling. Whisk in the lemon pie filling or curd until smooth. The mixture should look glossy and thick.

Fold in the cake mix. Add the lemon cake mix and stir with a spatula until just combined. A few small lumps are fine. Avoid overmixing so the crumb stays tender.

Pour and level. Scrape the batter into your prepared pan and smooth the top with the back of a spoon or an offset spatula.

Bake. Bake for 25–32 minutes, depending on your pan and oven. The top should spring back when lightly pressed, and a toothpick inserted near the center should come out with a few moist crumbs.

Cool. Let the cake cool in the pan for 10 minutes, then lift it out using the parchment and set it on a wire rack to cool completely. This prevents sogginess and helps the texture set.

Finish and serve. Dust with powdered sugar or drizzle with a quick lemon glaze (1 cup powdered sugar mixed with 1–2 tablespoons fresh lemon juice). Slice and enjoy.