Thoroughly grease every fold of the lamb mold with melted 1 Tablespoon solid fat, then dust it with 2 Tablespoons sifted breadcrumbs or flour. Tap the mold gently on the counter to remove any excess. Preheat the oven to
320 °F with upper and lower heat. Take 3 eggs out of the refrigerator one hour before baking. Crack them into a large bowl and beat with the granulated sugar using an electric mixer. Start on lower speed, adding 1 ¼ cups granulated sugar gradually, then increase the speed to high. Beat for at least 5 minutes, until the mixture becomes pale, light, and airy.
Reduce the mixer speed to low. Add ½ teaspoon vanilla extract and 1 ½ Tablespoons lemon zest, then gradually mix in 1 cup buttermilk and ¼ cup vegetable oil.
In a separate bowl, combine 2 ¾ cups all-purpose flour and 1 teaspoon baking soda. Gradually add the mixture to the batter, mixing slowly to prevent lumps.
Pour the batter into the prepared mold immediately. Fill the mold to about 1¼ inches (3 cm) below the edge, as the batter will rise during baking.
Place the filled mold in the preheated oven and bake for 1 to 1¼ hours.
Check for doneness by inserting a wooden skewer into the lamb. If it comes out clean, the cake is ready. If batter sticks to the skewer, return the cake to the oven for 5 more minutes, then test again.
Let the baked lamb rest in the mold for 10 minutes, then carefully turn the mold over and remove the cake.
Allow the lamb to cool completely. Dust with 2 Tablespoons powdered sugar, tie a ribbon around the neck in cheerful spring colors, and place it on a serving platter.