The 8.20pm show, which saw the 2008 X Factor winner take to the stage to sing her latest single 'Broken Heels', pulled in 5.49m (21.3%) - beating last week's effort of 5.18m (20.4%).
The regular live show, which aired between 6.30pm and 7.30pm, pulled in 5.59m (23.9%).
Also on BBC One last night, The National Lottery: In It To Win It had 5.85m (23.8%) at 7.30pm, and Casualty logged 6.01m (23.7%) between 8.50pm and 9.40pm.
Over on BBC Two, The Legacy Of Lawrence Of Arabia put in 1.86m (7.3%) during the 8pm hour, 1.59m (6.6%) watched the live snooker between 9pm and 10.30pm, and Heroes interested 800k (4.1%) immediately afterwards.
Take Me Out grabbed 4.44m (17.9%) for ITV1 at 7.30pm, then 5m (19.5%) tuned in for All Star Mr & Mrs at 8.30pm. Renee Zellweger movie Bridget Jones's Diary averaged 3.15m (14.5%) between 9.30pm and 11pm.
The Parent Trap managed 1.83m (7.5%) for Channel 4 between 6.30pm and 9pm, then 2.33m (9.3%) watched Celebrity Big Brother during the 9pm hour.
Five's CSI and CSI: New York pulled in 1.2m (4.7%) and 2.4m (10.5%) at 8.45pm and 9.45pm respectively.
Overall, BBC One dominated primetime with an average share of 22.3% to ITV1's 17%. Channel 4 was third with 7.3% (+1: 0.9%), followed by BBC Two with 6.4% and Five's 6.1%.
BARB ratings data supplied by Attentional