hello I'm designing a PLL and I need to simulate the frequency on the time domain as below

You can start with an open loop VCO, such as a ring oscillator. You should save the output waveform outside your simulation and measure it using other software, such as python scripts or matlab. You could also design a VerilogA block to continuously measure the output frequency of an oscillator.

can i do it on ngspice? because i'm designing pll on xschem

As far as I know, you can measure the frequency with ngspice with built-in commands,but not cycle by cycle, which is needed to make this curve. You could make a VerilogA block to convert the instantaneous frequency to a voltage, but then you need to learn how to use VerilogA with ngspice, and then design it by yourself.