In a large bowl put the sifted flour, salt, baking soda and lemon zest, then mix them well with a spoon. Set aside.
In the bowl of a stand mixer, whisk the butter, oil and sugar until creamy.
Add the egg and lemon juice.
In a big cup, mix with a spoon the buttermilk, vinegar and yellow food coloring (use enough to obtain a bright yellow color).
Pour both flour and buttermilk mixture into the bowl ( with the butter mixture). Make sure to strain the buttermilk mixture. Mix well until smooth.
Pour the butter in a muffin pan lined with cupcakes liners (2/3 full).
Bake in a 350°F preheated oven for about 20 minutes.
Let cool completely.
Prepare the lemon cream cheese frosting by mixing all the ingredients until smooth.
Place the cream cheese frosting in a piping bag and pipe the frosting on top of each cupcake.
Sprinkle with colored sprinkles (optional).