Preheat oven to 350 degrees F. Line muffin pan with cupcake liners and set aside.
In large bowl, beat together butter and sugar with electric mixer until light and fluffy, about 3 minutes.
Add eggs, one at a time, beating until combined.
Add vanilla, and beat until combined.
In separate bowl, combine flour, baking powder, and salt.
Add flour mixture to butter/sugar mixture.
Combine milk, lemon juice, and lemon zest.
Slowly add into batter, until just combined.
Scrape down the sides and make sure all is completely mixed.
Evenly distribute among 12 cupcake liners.
Bake in preheated oven for 18-20 minutes, until toothpick comes out clean.
Cool completely before frosting.
To make the frosting:
Beat together butter and powdered sugar, until well combined.
Add cream/milk, lemon juice, lemon zest, and vanilla, beating until well combined.
Add more milk if needed for desired consistency.
Beat for another 2-3 minutes, until the mixture is light and fluffy.
Frost the cupcakes either with a knife or by piping it on. Leave a little extra frosting for applying the jelly beans.
Sprinkle with "grass", then use remaining frosting to stick jelly beans onto the grass. I just put a small bit of the frosting on the back of each jelly bean to ensure they stuck well.