Lemon-Lime Tea Cakes

Ingredients

• 2 large eggs
• 1 1/3 cups sugar
• 1 cup all-purpose flour, (spooned and leveled)
• 1/4 teaspoon coarse salt
• 1 teaspoon finely grated lemon zest, plus 1 teaspoon fresh lemon juice
• 1 teaspoon finely grated lime zest, plus 1 teaspoon fresh lime juice
• 1 lemon (ends cut off), very thinly sliced and seeded
• 1/2 cup (1 stick) unsalted butter, room temperature, plus more for pan