Standard brownie recipe

I have several brownie recipes but I'm calling this 'standard' because I found two recipes from two different sites yet both are exactly the same, except for the vanilla and salt. Here are the links:
Centrecutcook: http://www.centercutcook.com/the-best-brownies/
Iambaker: http://iambaker.net/homemade-brownie-mix/

This version is from the first link but I've added comments from the second link.

Ingredients
Wet
1/2 cup melted butter, cooled
2 eggs
2 tsp vanilla extract (or 1 tsp)

Dry
1 cup white sugar
1/2 cup white flour
1/4 tsp salt (or 1 tsp)
1/4 tsp baking power
(optional: my addition) 1/4 cup chopped nuts and/or 1/4 cup chocolate chips and/or 1/4 cup raisins)

Method
1) Prepare a 8*8 inch pan with parchment, or butter and coat with thin layer of flour. I prefer parchment. If I leave a bit of overhang on the side, it makes the brownie easier to remove.
3) Mix the wet. Mix the dry. Combine.
3 Pour into the prepared pan. Bake at 350 deg F (176 deg C) for 25 to 30 mins (check after 22 mins). A skewer inserted should come out mostly clean with some crumbs. You want it slightly under cooked because it will continue to cook in the pan.
4) Cool in the tin for at least 10 minutes, then remove to wire rack to cool completely before cutting. Otherwise, it will just be a crumby, fudgey mess.

Recipe feedback: I didn't have a square pan and used my 5*7 inch pyrex pan. On my non-fan forced mode in the oven, it took 31 minutes (checking after 25) and it was just the tiniest bit of wobble. I let it cool in the pan for 30 minutes then on a rack completely for 2 hours before cutting.

I realised that it cannot stay in the pan for too long as it continues to cook on the sides but not the middle, but if u take it out too soon, it collapses. The sugar crystallises on cooling, making the top crispy and hard to cut into so cut carefully.