Ronaldo was in the president's box as his recently-acquired Valladolid conceded in stoppage time to lose 1-0 at home to Alaves.
The Brazilian World Cup winner recently bought a 51 per cent stake in the promoted club and took his seat in the stands at the Estadio Jose Zorrilla for the first time on Sunday.
But the three-time world player of the year could do little as Ibai Gomez struck in the third minute of added time to snatch a dramatic late victory for the visitors.
Valladolid, yet to win since returning to the top flight, had looked like clinging on for a point when Gomez struck on a counter attack.
Toni Villa had missed at the other end just moments earlier.
In Barcelona, Espanyol maintained their positive start to the season with a 1-0 win over Levante to jump up to fourth.
Elsewhere, Angel struck twice in the first half as Getafe claimed a 2-0 win over Sevilla in a compelling clash at the Ramon Sanchez Pizjuan Stadium.
The striker netted within three minutes of the kick-off and doubled the visitors' lead just before the interval, after an error from Ever Banega.
"I'm very happy on a personal level (but) I live off my teammates," Angel said.
"All the goals that I score are thanks to them.
"We have to go step by step, to play each Sunday as if it were a final."
Sevilla's Wissam Ben Yedder has a goal ruled out for offside with the aid of the video assistant referee.
Getafe are fifth on seven points while Sevilla are three points further back in 11th.
Carlos Bacca scored the only goal as Villarreal won 1-0 at bottom side Leganes.
The Colombian headed home after 65 minutes from a Miguel Layun cross, earning his side their first win of the campaign to go 13th.
Leganes were left with just a point from four outings and still awaiting their first victory.