Open Photoshop and create a new document. I used 2560x1440 pixels. Then with the Gradient Tool (G) fill the background with a radial gradient with 2 shades of purple (3d2626) Lighter and (060404) darker.
With the Elliptical Marquee Tool (M) create an ellipse selection. Add a new layer and select the Gradient Tool (G). Use black and a very light grey for the colors. Fill the ellipse selection with the radial gradient. Use the image below for reference.