Meringue buttercream
My first time meringue buttercream was ideal because of step-by-step instructions by Taste Goblet Blog. I added some nutella for flavor.

3 egg whites
1/2 cup sugar
150g butter, softened to room temperature
1/2 tsp pure vanilla or any flavoring you want

Place sugar and egg whites in the heat-proof bowl of an electric mixer. Set bowl over a pan of gently simmering water, and whisk until sugar has dissolved and egg whites are hot to the touch, about 3 minutes.
Transfer bowl to mixer stand. Beat on high speed with whisk until mixture formed stiff and glossy peaks, about 10 minutes.
Add the butter, one piece at a time, and beat until incorporated after each addition. Don't worry if the buttercream appears curdled after all the butter has been added; it will become smooth again with continued beating.
Beat the mixture on medium-high speed until it thickens. This can take anywhwere from 7 to 15 minutes. Add vanilla, and beat just until combined.
