Make a simple syrup by combining 1 cup granulated sugar and 1 cup of water in a pot over medium heat. Simmer, stirring, until the sugar has dissolved fully Set aside to cool a bit.
If you haven't already done so, squeeze enough lemons to equal 1 cup lemon juice. Place the lemon juice and simple syrup in a pitcher, then add 4 cups of water (or more to taste). Stir to combine.
Store leftover lemonade in an airtight glass container in the fridge for up to 5 days.
Notes
How to choose lemons: Not all lemons are created equal. The best lemons for lemonade feel heavy (ie, full of juice). I prefer to use Meyer lemons for lemonade as they are milder and sweeter, but any type of lemon will work.
Roll the lemons before juicing. Give each lemon a firm roll on the countertop before juicing it to help break down the membranes inside. This will give you more juice!
Make the simple syrup! Don't skip this step. For a smooth and balanced sip, you DO NOT want grainy sugar in the lemonade. A brief dissolving of water and sugar will result in sweet sugar water to perfectly incorporate into the lemon juice.
Chill. You can totally drink lemonade as soon as it's stirred together, but I like to chill it for at least 30 minutes before serving. Or, serve it over ice if you can't wait.
Adjust the sweetness. I strongly recommend tasting the lemonade as you go and adding the dissolved sugar slowly. Stop when you've reached your perfect sweetness level.
Make it a cocktail! Use lemonade as the mixer in a summery cocktail. Pair it with bourbon, vodka, or gin.
Or a mocktail. Add a splash of sparkling water to turn this into a fizzy lemon mocktail, then garnish wtih a slice of strawberry or a sprig of mint.
Double the batch. You can easily double or triple this recipe to make a lot of lemonade!