Place ricotta over a strainer lined with cheesecloth. Allow ricotta to drain for 10 minutes while you prep remaining ingredients. (Skip this step if you purchased strained ricotta or ricotta seems dry.)
In a large bowl, whisk together flour, oat flour, baking powder, and salt. In another bowl, beat together egg yolks, Meyer lemon zest, and sugar until smooth. Add Meyer lemon juice and milk. Mix until well combined. Add wet ingredients to large bowl with dry ingredients. Stir until just combined. The batter will be lumpy.
In another bowl, beat egg whites to stiff peaks. Add egg whites to batter in three additions, gently folding egg whites to distribute. The batter will loosen and smooth out as egg whites are added.
Lightly grease griddle or large skillet with butter or ghee. Set over medium heat. Once griddle is hot, pour in ⅓ cup portions of batter. Cook until bubbles begin to form on surface, about 2 minutes. Flip pancake over with spatula and cook other side until lightly browned. Repeat with remaining batter. Adjust heat accordingly if pancakes are browning too fast.
Serve pancakes warm with chilled candied lemon slices and maple syrup. If desired, drizzle served candied syrup over pancakes for additional sweetness.