In terms of tree representation and CG format, this type of sentence had to be manually revised because if it seems obvious for any human that the clause in quotation marks is the direct object of the verb in the main clause: pergunta , it is not that obvious for the parser since the subordinating conjunction que is not present.

In CG  format, the sentence would be:

Quantas  [quanto]  <interr> <quant> DET F P @>N
Laura=Pausini  [Laura=Pausini] PROP F S/P @SUBJ>
estão  [estar] <fmc> V PR 3P IND VFIN @FMV @#FS-ACC>
aqui  [aqui] ADV @<ADV
esta  [este] <dem> DET F S @>N
noite  [noite] N F S @<ADVL
$?
$"
$,
pergunta  [perguntar] <fmc> V PR 3S IND VFIN @FMV
$.

The external function of the clause (@#FS-ACC>) is indicated in the main verb of the accusative clause (estão). In tree representation, the clause in quotation marks will hold the function ACC:

STA:fcl
ACC:fcl    Quantas Laura Pausini estão aqui esta noite
,
P:v-fin    pergunta
.

Refer to the correspondent graphic tree:

See sentence C142-1 for a similar case.