• Preheat oven to 400˚F (200˚C). Line 12 muffin tins with non-stick liners or grease with oil.
• In a large bowl, rub the lemon zest into the granulated sugar.
• Mix in the flour, baking powder, and salt.
• In a medium bowl, beat together the ricotta, olive oil, lemon juice, milk, eggs, and vanilla extract until light. Fold the wet ingredients into the flour mixture until just combined with no streaks remaining. Be careful not to overmix.
• Scoop the batter into the prepared muffin tins about 3/4 full. If using almonds, top the muffins generously with coarse sugar, followed by a few sliced almonds. Place in the preheated oven.
• Cook until lightly golden and a toothpick comes out clean when inserted in the center, about 14-16 minutes.
• Allow to cool in tins for 5 minutes before removing to wire rack.

To Make the Lemon Glaze:

• In a medium bowl, whisk together powdered sugar and lemon juice until combined and no lumps remain. If too thick to drizzle, add a little more lemon juice. If too thin, whisk in a little more powdered sugar.
• Drizzle over room temperature muffins if not using the sliced almonds. Allow to set for a few minutes, and serve the day they are prepared.