gulpfile.js

var gulp = require('gulp')
var postcss = require('gulp-postcss')
var tw = require('@tailwindcss/jit')
var ap = require('autoprefixer')
var sourcemaps = require('gulp-sourcemaps')
const cleanCSS = require('gulp-clean-css')
var clean = require('gulp-clean')
var nested = require('postcss-nested')

gulp.task('clean-css', function (done) {
  return gulp.src('../static/css/*.css', { read: false }).pipe(clean({ force: true }))
})

gulp.task('css', function () {
  return gulp
    .src('css/**/*.css')
    .pipe(sourcemaps.init())
    .pipe(postcss([tw('./tailwind.config.js'), nested(), ap()]))
    .pipe(cleanCSS())
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('../static/css/'))
})

gulp.task('watch', function () {
  gulp.watch(['./templates/*.html', './css/*.css'], gulp.series('clean-css', 'css'))
})

gulp.task('default', gulp.series('clean-css', 'css',  'watch'))

Used by just running gulp, not a package.json script.