Beat the eggs and sugar in a large bowl until the sugar is completely dissolved.
Sift the flour, salt, and baking powder together in a separate bowl, then add it to the egg and sugar mixture. Whisk until just incorporated.
Add the olive oil, milk, and lemon zest and whisk until well combined.
To achieve the spongy texture of a Spanish magdalena, you'll need to let the batter rest in the fridge. Cover the bowl with plastic wrap and leave in the fridge for 1 hour.
Meanwhile, preheat the oven to 480°F (250°C). Line a 12-hole muffin tray with paper wrappers.
Fill the wrappers ¾ of the way with the chilled batter. If you'd like, sprinkle a pinch of sugar on top of each muffin to form the sugary crust that is typical of Spanish magdalenas.
As soon as you put the muffins in the oven, lower the heat to 400°F (200°C). Bake for 15 minutes on the middle rack. Test with a toothpick in the middle of a muffin to make sure they're cooked through. Don't open the oven until you think they're ready!
Let the magdalenas cool in the pan for at least 5 minutes, then enjoy them warm or let them finish cooling on a wire rack. Enjoy them with a hot cup of coffee!