I get this question quite a bit.
I usually summarize with "A brownie without the cocoa powder" but they are much more than that.
So let's start with a brownie, a blondies' closest sibling. A brownie is typically all chocolate and made by either melting a, hopefully, high-quality chocolate into liquid form or using cocoa powder. The resulting textures are either fudgey or cakey respectively. I personally prefer a moist cakey brownie but can definitely appreciate a fudgey brownie as well.
A blondie however usually starts with brown sugar. At Blondery, we use light brown sugar but you can use whatever you want. If you want more of a molasses flavor, I would opt for dark brown sugar.
Some would describe a blondie as a butterscotch base. I like to sound of that but I'm afraid most people relate butterscotch to those candies that ladies in church gave out. Quaint but not quite the flavor profile I am looking for in a blondie. Although, the definition of butter scotch is melting butter with brown sugar (remind me to share a butterscotch pudding recipe with you all one day, mind-blowing!).
Anyway, if I was to answer technically: a blondies is a butterscotch based, typically square, dense pale-colored cake. At Blondery, that is just the beginning. We then add semi-sweet chocolate chips to the batter and top it off with a salted caramel jam, pink Himalayan sea salt and toasted pecans.
We have taken it a step further and created a collection of blondies including a vegan sweet potato blondies and a chocolate peanut butter blondie that is high in natural protein.
So that's a blondie!