
A Three Frame Sandwich.
aka
Serif Forum Background as shown by Sam and fixed for me by Andy H.
1. Page has no Master Page.
2. Select a color in Page Properties > background tab > background color drop down box.
3. Create a Quick Shape rectangle. Use the node handle to round the corners. Fill the QS with a coordinating color.
Then, right click and select Filter Effects. Set ColorFill to normal or multiply.
Set Feather to 30 opacity and 15 blur.
4. Create a second QS rectangle, round the corners and fill with white. Position on top.
5. Finally, create a text frame on top of both.

Sam’s screenshot below.